By on September 6, 2011

It actually comes with a little book too!

Patrick writes:

Hi Sajeev,

Avid daily reader of the site but infrequent commenter… Pony Cars and old Volvos sometimes drag me out of my shell but I have a couple questions about my wife’s car and I wanted to see what you and others might think.

We’ve got a 2007 3.5L Impala with 60,000 miles on it and it is due for an oil change and checkup:

1. Am I crazy for trusting the car’s computer to tell me when to change the oil? The car monitors oil life and reports a % of oil life remaining and nags me when it’s time for an oil change. The owners manual doesn’t specify a mileage interval instead advising to change it when the car’s info center says it’s time. It typically runs from 8K to 11K miles between changes so far.
The dealer would rather us get it changed at every 3K and are so desperate to get their fix of oil change traffic that they offer a “free tires for life” deal if you stay on the 3K schedule with them. Factoring in the cheap tires they get at cost that they’d slap on there, they’re most certainly coming out ahead (which is why they do it, of course); factoring in the extra services and the mounting and balancing fees for those free tires, it’s probably a wash for me so I’ve declined and followed the car’s schedule instead of there’s as
I’d rather save up for that next set of tires than have to go in to the dealer 3 or 4 times as often.

Now, I know I don’t have to take it to the dealer and while I do almost all of my own service, repairs and upgrades on my car, wrenching on our utilitarian transportation-mobile isn’t nearly as rewarding and I don’t mind throwing the Chevy place a bone every once-in-a-while, especially since their service isn’t much more than the quicky oil change places and, theoretically at least, they should be intimately familiar with this generation of Impalas – plus if and when it comes time to trade it in or sell it, I’ll have nice official looking dealer records to go with it.
I figure GM did their homework with the oil monitoring system and I’m comfortable with longer oil change intervals – I do 6K ~ 7.5K on my Mustang (’96 GT) which has 130K+ on it and oil still comes out clean and when I had the valve covers off last year, the top of the heads were clean as a whistle. With the Impala PCM monitoring temps and driving usage and whatever other variables it factors in, I’m willing to let it ride a little longer if GM says it’s OK. Have you heard anything that would give me reason to believe otherwise?

2. When I realized 60K was coming up, I rushed to the owners manual to see what expensive work the dealer was going to want to do – then I remembered this wasn’t a European car and there was nothing other than greasing door hinges and locks and inspecting a few wear items that needed to be done. I did notice that the book calls for a fluid replacement at 150K miles for the 4T65-E transmission (or at 75K for severe duty). After reading some of auto transmission horror stories here but not being aware of any endemic problems with GM’s transverse V6 transes is 150K too long to go, should I plan on doing that sooner? 100K, 125K, if we still have the car that long or is GM pretty close to the mark on that?

Sajeev answers:

I never thought that answering a GM W-body question would be a breath of fresh air in my Piston Slap queue, but well, here we are. Patrick has valid and relevant questions to  anyone with a less than desirable ride that does the job and keeps you mobile. You know, cars for the vast majority of us!

So let’s do this thing:

Question 1:
by all means, ignore the dealer when they pull the “free tires for life” and 3k oil changes. Like you said, I wouldn’t leave them entirely, as their pricing should be comparable to the quickie oil change places, but you need to get the playing field level: remind the service writer that you’re familiar with the phrase RTFM. And you expect them to treat you accordingly. The “do this to be more proactive” tactic you mentioned works on some people, and that’s fine. But that’s obviously not you or anyone else here. It’s all about treating the customer with respect.

I trust that oil life meter after years of questioning it via dipstick eyeballing. Now that I run synthetic oil (in cars that never officially required it), I change the oil after about 180% of its life: that is, resetting it once and then changing it when its 80% used. It seems like the smartest way to not waste good oil, and my driving conditions merit it: lotsa traffic, heavy engine loads (aftermarket stereo, A/C) and brutal Gulf Coast summers. The 180% mark turns into 6000-8000 miles of my commute. Which is fair for synthetic oil.

It works for me, maybe I should take my used oil examined to a lab to prove it to everyone…but I don’t really care since it’s been working for well over 175,000 miles on my very, very healthy Lincoln Mark VIII motor. Healthy enough to let me (cautiously at first) trust the life meter on other cars too. More to the point, your driving conditions can and will vary.

Question 2:
there are no endemic problems with this GM transaxle that I know of, but I would still change the fluid before it hits 100k out of principle alone. Again, this depends on your driving/climate conditions, but my gut tells me you should change the fluid according to the severe duty schedule in your owner’s manual. Transaxles in general deserve the “severe” fluid service schedule, and this Impala sounds worth it. Be it a flushing machine or the conventional drain and filter replacement, just make sure all the fluid is changed…don’t let old fluid rest in the torque converter and mix in with the new stuff.

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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48 Comments on “Piston Slap: RTFM FTW...”


  • avatar
    tankinbeans

    I’m guessing that this means I, too, can skip the dealer’s “everybody drives under severe conditions so we recommend 3k changes” schtick. I brought it in for the first change at 3700 and their sticker thingamablobber told me to come in again at 6700, but when 6700 came around I looked at the dipstick and the oil still looks new and slippery (if there’s even a way to eyeball that). My friend, who is fairly mechanically inclined, said I’m probably safe waiting until 8700, but I’ll check again at 7700 just to look at it. My driving is hit and miss with some being lots of longer >10 miles (outside of severe per the schedule) and others being more short distances <10 miles (inside of severe per the schedule.)

  • avatar

    Let’s see if this posting images thing works for regular folks.

    Nope, how about a link then…

    Dogbert on Manual

    http://dilbert.com/dyn/str_strip/000000000/00000000/0000000/000000/20000/1000/100/21191/21191.strip.zoom.gif

  • avatar
    seabrjim

    15,000 miles on synthetic, pick your brand. Walmart super tech is the cheapest full synthetic out there. I think its made by texaco. change the filter at 5,000 and 10,000 using another 10 or 12 oinces of oil and the a total oil change at 15,000. never had a problem. I do the same with my 2011 mustang gt and it see’s the redline often. Synthetic flows right away in the winter and doesnt shear in the summer and its still cheaper than changing regular oil every 3,000.

  • avatar
    DC Bruce

    Jeez, what a racket!

    The old air-cooled VWs required 3,000 mile oil changes because: (1) the engine used lube oil as a coolant and (2) the engine had no oil filter! I installed an oil pressure and temperature gauge in my mildly modified Karmann Ghia and observed that oil temperatures in the summer ran around 270 degrees F. I also used 40 weight oil in the summer and had a bolt on additional oil reservoir that both added to the engine’s oil capacity and provided a modest additional cooling. If I had kept the car longer, I would have added an outboard oil cooler and filter.

    Today’s “service reminder indicators” I think do a good job of accounting for the car that spends most of its time idling and creeping in traffic and one that spends most of its time at 65 mph. Using a mileage-based formula, the car sitting a lot in traffic is not going to get its oil changed frequently enough.

    It probably does not make sense to use the “severe duty” schedule in the manual for things like changing ATF. Stop and go traffic is much harder on an autobox than cruising down the highway.

    As for the free tires deal, IMHO, no matter what you drive, money spent on good tires is money well spent. After all, it’s your tires that stop you car and turn it, so you kind of have an interest in seeing that response from the car when you apply the brakes or turn the steering wheel. Not to mention that, in extreme situations, like hitting an unexpected chuckhole, you’d probably prefer that the tire not fail instantly.

  • avatar
    slance66

    I always believed that J*ffy Lube invented the 3k oil change interval. On the other hand, BMW wants me to change my oil at 15,000. While it is synthetic, that strikes me as pushing my luck and then some. So I’ll halve it and go at 7,500.

    My father in law has a 2005 CR-V due for its 90k. Looked at the list and told him to get separate quotes for the services we won’t attempt (rear differential and transmission fluid) and that I’d change his plugs, air filter and cabin air filter. Those package 60k, 90k etc. services always seem to have some dealer padding in them.

    • 0 avatar
      Russycle

      I just changed the rear dif and (manual) trans fluid on my Element. Same drivetrain, very easy to do if you want to avoid the dealership.

    • 0 avatar
      mswarms

      Since 1975 I have run a synthetic guaranteed for 25,000 mile oil drain intervals (Amsoil). The first four or five times I sent the drain oil out for analysis and the report verified that the oil was still okay every time. I finally stopped testing and just did the oil change. Because synthetics do not oxidize like petroleum oils, and most “dirt” in oil is the result of oxidation, the key to long oil drain periods with synthetics is a combination of the the quality of the additive package and the filtration. High quality synthetics, such as Mobil 1 have superb molecular structure and excellent additives, so they can handle extremely long drain intervals. since a small percent of contaminants do enter the crankcase through combustion bypass it is critical to use a premium, preferably depth type filter. If you are worried still, use a synthetic product with an extended mile warranty (Mobil 1 has a 15,000 mile, Amsoil has a 25,000 mile) and change the filter at the halfway point.

  • avatar
    APaGttH

    There has been numerous papers, stories, articles and reviews of the GM oil life management system (I believe Honda has a similar system).

    The GM system doesn’t have a “sensor,” a common myth among the masses. The GM system evaluates driving style, load, ambient conditions, etc. etc. and monitors the anticipated life of the oil based on that soup of data. It isn’t counting miles per se, it isn’t testing the oil or has some magical sensor that acts as a chemistry lab looking for varnish, sludge and microscopic metal bits. It is all complex math based on the data streaming into the OBDII.

    Take a GM product out for a couple of days of hard lapping and watch that oil life monitor percentage plunge like a rock off a bridge. Gently drive it at 40 MPH on flat land on 70 degree days of San Diego avoiding stop and go and hard loads and you may change the oil because you hit 12 months, not the end of useful oil.

    Several pubs, bloggers, etc. etc. have followed the oil life monitor, drained the oil and sent it out for testing to see how accurate it was. All labs have concluded the same thing. Damn accurate actually, if anything conservative based upon there is probably a bit more life left than actually indicated.

    When I’ve owned GM products in the last 15 odd years I have followed the oil life monitoring system and the recommendations in the owner’s manual for additional service. That’s all I need to do to keep the warranty going. Anything beyond that is over kill and probably wasting bucks.

    If you’re still nervous, then switch to full synthetic and follow the monitor. You’ll save money and provides a no-brainer peace of mind on when to change the oil. Just make sure when the oil is changed the shop actually resets the monitor – that is probably the biggest mistake made. If you find you forget than go to a 3K to 5K mile chance cycle and then reset.

    • 0 avatar
      patman

      That’s pretty much what I figured and good to hear that the tests match up with the estimates. GM can do some dumb things but they have some smart engineers. I’m fine going with the computer’s schedule but wanted a little reassurance for when the dealer starts laying on the hard sell.

      • 0 avatar
        geozinger

        My experience is similar to Hypnotoads. At first I didn’t trust the old monitors, but after several years and several different models, I had a non GM service guy test my oil and visually inspect one of the motors. It was fine.

        OTOH, my one brother in law is not mechanically inclined (I call him mechanically reclined) changes his oil every 3-4K. And does other maintenance by the book. I’ve bought a couple of cars off of him, and they are like new, even if they’re seven years or older when I buy them from him.

  • avatar
    Educator(of teachers)Dan

    “We’ve got a 2007 3.5L Impala with 60,000 miles on it and it is due for an oil change and checkup”

    Jeeze I already feel sorry for you having such a sad little low po motor. Anyway – follow the monitor. I work for a school district and we actually follow the oil monitor on our vehicles that have them. Yes I have noticed that driving style and destination affects the oil life, gosh for some reason the oil changes come up sooner when I’m driving the vehicle!

    Auto trans I’d follow the severe duty schedule just to cover my butt. Auto transmissions are like children, they tend to misbehave when ignored.

    • 0 avatar
      patman

      Only 211hp, I know! Actually, it’s plenty enough for things like accelerating up on-ramps and passing slow-pokes on two lane highways but you have to wind it up to wring it out of it and it doesn’t sound like it really wants to do that. Conspiring against you is the transmission programming which wants to shift like you’ve got a low RPM big block torque curve instead of a smallish-for-a-big-car V6 curve.

      I wish it had the old 3800 in it though, that motor in our ’01 LeSabre is much friendlier and got better mileage too. It only had 190 horses, if I recall, but felt much bigger than the modest difference in displacement between the two would have you believe. That car is still chugging along happily in my stepson’s hands.

    • 0 avatar
      potatobreath

      The 3500 has quite a bit of twist. I’ve watched a coworker light up the front tire for a few blocks. I can only imagine what the 3900 would do. I think the sluggishness is with the transmission programming, but given the right coaxing with the right foot, she goes pretty good. The corporate High Feature 3.6 L in the new 2012 models is punchy too. Sounds kinda like a supercharger whine if you give her some gas. ;)

      • 0 avatar
        Educator(of teachers)Dan

        Ah good ol’ VVT. I’d like to drive an older W-body LaCrosse with the 3.6VVT and the 4-speed auto back to back with a new Impala with the 3.6VVT and 6-speed auto just to feel the difference. I was amazed when Buick put the 3.6 in the higher trim levels of the “bug eyed” LaCrosse and then harnessed it to that old school transmission.

      • 0 avatar
        doctor olds

        @Ed Dan- The 3.6L HFV6 has never been available with 4 speed auto.

        We arranged a drive opportunity for journalists comparing Pontiac G6’s with the HFV6 vs the 3.9L HVV6 (High Feature vs High Value)at the Milford proving grounds. Most could not tell which engine had the DOHC.

  • avatar
    patman

    175K on a 4.6L? That’s only just getting broken in! Somewhere there’s pics of a 200K+ T-bird block with the factory crosshatching marks still visible.

    Thanks for taking the question. Shockingly, the Impala hasn’t blown up yet, despite my cavalier attitude towards oil changes.

  • avatar
    suspekt

    The 3.5 VVT puhsrod V6 is a great motor. I swear it feels like it puts out 300lb/tq from idle to 3,000rpm.

    It has turned out to be one of my favorite things about our car.

    Does anyone know if it was ever paired with a 6 speed auto?

    Mine does 30mpg HWY all say and honestly doesn’t seem to need the 2 extra gears but I swear the 3.5 could turn 1,200rpm and still provide smooth acceleration at speed.

    Love that motor.

    • 0 avatar
      86er

      Does anyone know if it was ever paired with a 6 speed auto?

      No, but the 2012 model will have the 3.6L direct injected motor with the 6-speed:

      http://www.thetruthaboutcars.com/2011/07/2012-impala-302hp-30mpg-25645/

      No idea if that will be an improvement or not.

    • 0 avatar
      patman

      My experience has been the opposite – I liked the 3800 in her old ’01 LeSabre better. It felt much bigger in the 1000~2000 RPM range where it spent most of its time.

      I’ve tried hard to get 30 on the highway with the Impala and I always come up a little short (and I even got 30 MPG out of the Mustang GT once). The LeSabre did better around town and on the highway – 30 was no sweat for it on the interstate.

      • 0 avatar
        APaGttH

        I’m with you – I think the 3800 has more low end punch than the 3500.

      • 0 avatar
        Educator(of teachers)Dan

        At least one member of the B&B thinks that GM may have lied about the amount of torque the 3800 makes, that it’s higher than it is on paper. Damned if I can remember which member though.

      • 0 avatar
        mazder3

        HoldenSSVSE?
        http://www.thetruthaboutcars.com/2011/02/piston-slap-sensible-shoes-in-need-of-blue-suede/#comment-1719024

      • 0 avatar
        Russycle

        Dan, I remember when the Chrysler “cab forward” sedans first came out, one of the mags did a comparison with a GM sled sporting the 3800. The Chrysler mill had better torque and HP numbers, but the GM vehicle out performed it in every driving test. I wouldn’t be surprised if GM was sandbagging.

        I spent a week with a 3.8 liter Bonneville, I can understand the nostalgia for that motor.

  • avatar
    mikey

    Here in our Southern Ontario climate my 09 Impala 3.9, gets a oil and filter every 50000 klms {3500 miles} I rotate the tires every second oil change.

    My summer car, an 08 4.0 Mustang gets two oil and filter changes for the seven months its on the road.

    Is it overkill?…Probably, but its what I’m comfortble with.

    Now..Talking about the 3800. My former summer toy was a Firebird. The 3800 was all you could ask for in a V6. As far as the rest of the car?….Not so much.

    I love my Mustang, its just too bad you can’t get one with a GM 3800 V6.

    Impala gas consumption? On the highway in the USA I can average 27 to 29. The 2000 Firebird would give an honest 25 mpg. I got to work all the math but I estimate I’m getting 24 to 25 with the Mustang.

    • 0 avatar
      potatobreath

      Wikipedia said the Canadian Ford Essex 3.8 motor had its roots in the Buick 3800 (citation leads back to a really interesting article describing the two motors archived in the Wayback Machine). You could get the older Mustang with it. I like the styling of the newer Mustangs better though.

  • avatar
    Scoutdude

    Do not mess with the trans, if you must just drop the pan and change the filter. DO NOT have a transmission flush. It’s mixing the new with the old so you end up paying for fluid that ends up in the machine’s drain tank. The only thing the transmission flushing machine is good for is flushing the cash from your wallet.

  • avatar
    Steven Lang

    FWD midsized GM cars have been perfectly fine with the following intervals.

    Tranny fluid: Drain and fill every 30k.

    Oil changes: Stick to oil life monitor

  • avatar
    doctor olds

    Synthetic oil is more robust for very severe operation unlikely to occur on almost any street driven vehicle. It does offer other advantages, but a longer change interval than conventional oil is not one of them.
    If a vehicles does not specify synthetic oil, it is likely an un-necessary expense. The oil change intervals, even with conventional oils, is not based on breakdown of the oil itself, but contamination that can’t be reasonably filtered in-vehicle. It is imprudent to extend the change interval beyond the OLM indicator.

    • 0 avatar
      mswarms

      Sorry to disagree Dr. Olds, but the facts about Synthetic oils are not favoring you argument. According to Cummins Engine researchers, 75% of oil contamination it diesel engines comes from sludge, a by product of oxidation or breakdown of the oil, the rest is caused by 3 “outside sources, Air filtration bypass, combustion bypass and internal wear. In a gasoline engine Amsoil puts these figures at over 90% due to oxidation and the rest due to the other factors. Since high quality synthetics are so superior as to make oxidation negligible, the factors that make frequent drain intervals necessary are dramatically reduced, so you are able to continue using the oil. as for filtration of the contaminates that are present. Despite the inherent accuracy of GMs system, spectrographic analysis is still the most accurate determinate of an oils condition, rendering a breakdown of all components in the oil in parts per million, and if the spectrographic data shows oil to be well within tolerance after any given interval (In my case 25,000 miles consistently over four separate instances) then I am inclined to accept those results over a software program designed to guess without accepting intervening variables such as what kind of oil is being used.
      Today’s filter technology, including improved filter mediums and multi-layer designs hold more contaminates than ever before while simultaneously allowing improved oil flow. If you check the facts about the properties of synthetics, the nature of crankcase contaminates and the design technology of modern filters you will find that, not only are extended drain intervals possible, they are also completely practical. Not only can you safely drive the 15,000 miles recommended by Mobil 1, or the 25,000 miles warranted by Amsoil, but there are those out there who have gone far beyond those parameters. One over the road trucker has documented well over a half million miles on the same oil change and still going strong, by using a high quality synthetic and specialized bypass filters.

      • 0 avatar
        doctor olds

        @mswarms- Just sharing the facts learned by GM Powertrain engineering from millions of miles of vehicle testing and development.

        I also do have direct knowledge of the inside of engines run for long terms because the owner thought the synthetic oil would last 15,000 miles. It ain’t pretty.

        Over the road trucks are a bit different story because they have much larger reservoirs of oil. contamination takes a lot longer when you have gallons of oil rather than quarts.

        Who do you want to believe- the guy’s trying to sell you high priced oil, or the engineers who actually test their products far beyond what most imagine?

        BTW- how much does that spectrographic analysis cost? Isn’t an oil change cheaper than one analysis?

  • avatar
    ciddyguy

    Sajeev,

    Definitely a good call.

    A few years back, Tom and Ray of Car Talk fame had a caller who wanted to know if the usual 3000 mile oil change interval was too often as most cars seem to recommend upwards of 7000 miles (which was just beginning to be recommended back oh, 5-6 years ago) by the automakers and their conclusion was thus.

    With modern oils now readily available (G/H I think now) and with the additives they often contain, that 3000 miles, even on older cars is overkill, 7000 is good for most modern cars (today, more like 8-10K or perhaps more for some models) but for older cars, they split the difference and said about 5000 is a good, safe interval for those vehicles.

    That’s what I do in my ’92 Ford Ranger truck, I try to change it every 5000 miles and now it’s way overdue and needs it done SOON.

    But the thing is, conventional oils tend to break down much sooner than synthetics and I may go with synthetics in my next car if it’s new or nearly new.

  • avatar
    rudiger

    Reminds me of the recommended oil changes on the Prius. When the owner does them, it’s every 5k. But when Toyota service departments perform them under their free maintenance program, suddenly the recommendation doubles to every 10k.

    As to RTFM, lots of old Dodge Caravan owners and service departments did exactly that when Chrysler came out with the new, 4-speed A-604/41TE ‘Ultradrive’ automatic in the late eighties. The owner/service manuals said it was okay to use Dexron if the just introduced ATF+3 wasn’t available. Turns out that such a substitution didn’t work and resulted in lots of burned-up minivan transmissions. Chrysler made good on their mistake and replaced them under warranty, costing the company millions.

  • avatar
    flatout05

    I use synthetic and change it every 7500 miles. Why? Because I rotate the tires every 7500 miles as well. This way, I get it all done in a single 1-hour session in the garage, all while inspecting CV boots and brake pads and looking for miscellaneous leaks.

  • avatar
    Zackman

    Not much I can add to the discussion, as I change oil every four months – I stretched it out from every three a few years ago. I maintain my car according to the manual which I actually read! Now that my commute is 100 miles a day, I’ll probably stay with that, as once I hit the highway, it’s non-stop, full-speed-ahead for about 37 miles. My ’04 tranny acts up when it’s cold, though, and I’ll have to look into that – it slips a bit when starting off on occasion and “clunks” a bit. Any suggestions? Other than that, which is not a small thing, it’s been a great car for 84K miles.

  • avatar
    doctor olds

    Engine oil must be changed because of contamination that can not be practically filtered on board. GM’s engine oil life algorithm calculates the safe distance to drive before the next change by considering the number of engine revolutions at coolant temperatures. The system is generally very good at estimating when an oil change is necessary, though particularly dusty conditions can not be comprehended and require more frequent changes (RTFM).

    Synthetic oils do NOT allow any longer change interval than today’s regular oils, despite the word on the street. Both need to be changed when they become contaminated and should be changed by the time the oil life reaches zero% whether synthetic or not.

    Those who greatly extend oil change intervals under the false belief that the concern is oil breakdown and that synthetics last longer are living dangerously. Synthetic should be used only if recommended by the manufacturer, and must be changed just as often. It is a waste of money in an engine that doesn’t require it.

    • 0 avatar
      mswarms

      Guess we’ll just have to disagree Dr. Olds, While I respect your obviously extensive experience with automotive engines and their interiors in particular, I’m betting your tests do not include the brands I have mentioned. Here in Indy it is commonly known that every indy race car uses Mobil 1 oil, even when the car is sponsored by a competitors brand. There is a reason for that, not all synthetics are equal. The esther based products outperform the others by a wide margin. I am not an engineer or a scientist, but in 38 years of using the product I have seen the interior of more than a few engines and many with the Amsoil extended drain intervals. One VW Jetta for instance had the synthetic oil installed after a 3,000 mile initial run to assure proper wear in. After 75,000 mile, the pan was dropped and the valve cover removed for inspection. No mechanical difficulties, just a crew of mechanics who were curious enough to spring for new gaskets and put in an evening after work.Remarkably, the inside of that engine was as clean as the day it was assembled. The cross hatching was not even worn off the ends of the cam lobes. One main and one rod bearing cap were removed and there was no problems at all, just clean surface with no signs of wear or damage.
      Additionally, as far as the cost goes, if you contact Amsoil, they will tell you that their oil is fully warranted under normal driving conditions and there has not been one single claim in their history that turned out to be caused by the oil. I would suggest that you consider the possibility that while your experience and subsequent expertise in engine technology may be complete, your lack of understanding of lubricants, or at least gaps in your knowledge might probably lead to some wrong conclusions.

    • 0 avatar
      28-Cars-Later

      I run Mobil 1 in my 3800 Pontiac simply because I have seen inside of engines who ran it most of their lives and was impressed. After I bought the car used in 2010, I did a change with Mobil 1 and the computer was still showing 25% oil life after 12 months and around 7,500 (mostly highway) miles later. I agree the computer is a good indication as to when to change the oil, but unless mine malfunctioned it still felt the oil was acceptable at two and a half times the traditional 3,000 mile interval.

      • 0 avatar
        danio3834

        Just an FYI about the oil life monitor. It doesn’t know what type of oil you used in your engine, or the actual condition of it.

        It’s a program that takes inputs from various engine monitors and compares them to a table based on precalculated estimated oil life over mileage/cycles under those conditions.

        So if the oil life monitor took longer to count down during that period, it was because you either drove less or under lighter conditions or some combination thereof.

      • 0 avatar
        mswarms

        That raises an interesting question. If the computer in the car is calculating the oil change recommendation based on pre-set parameters such as conditions encountered while driving, and driving habits of the operator, then why would the product make any difference. The computer is unaware of the actual condition of the oil and is “guessing based on input from engine management systems such as temperature sensors, throttle position, shift sensors etc… I could see how this system could accurately predict the need for an oil change, but only if all oils worked and were affected equally under those conditions. One of Robbie Gordon’s crew mechanics told me that Pennsoil, their sponsor regularly sent a drum of Pennsoil synthetic oil to their shop. They would then pump out the drum and take the product away to use in their lawnmowers and such at home and refill the drum with Mobil 1. He said that the last time the Pennsoil reps came to the shop with samples of Pennsoils brand new synthetic. They were aware that the team was not using their product and they bragged that this time they would switch. They installed the oil on the engine mounted to the test stand. They bolted a freshly cleaned spotless oil pan on it first, then the ran the engine for thirty minutes. The test stand is capable of replicating all kinds of conditions, this time they placed the engine under a moderately sever load and heated the oil to 400 degrees, a pretty good test if the oil was up to it. It wasn’t. After 30 minutes the engine was stopped and the pan removed; the oil had began to break down and was all burned in the bottom of the oil pan leaving a large dark brown stain. The pan was then cleaned up and replaced on the engine. This time Mobil 1 was installed and the exact same settings were used for the same length of time. When the pan was removed after the second test both the oil and the pan were as clean as a whistle. While the story might be second hand, my own experience makes me believe it. So how does a computer, unaware of which oil, adjust for the difference?

      • 0 avatar
        danio3834

        mswarms, you’re exactly right, not all oils are created equal, and most oil life monitors can’t account for that.

        They’re programmed based on the recommended viscosity oil that meets the prescribed industry standards for the engine. Because the quality of oil can still vary, I stick to regular maintenance intervals instead of relying on the monitor.

        I know many people who were told by their OEM dealer service department to rely on the monitor, but have often found that if they wait until oil life actually counts to 0%, their oil level light comes on with it.

      • 0 avatar
        ciddyguy

        Danio3734, and MSwarms,

        I think you both are right, most oil monitors may not be able to tell what type of oil (synthetic or conventional, let alone which viscosity is in there), but they can sense how dirty it is, or in some cases what overall condition it may be in.

        That said, I think the main reason we even have these things is simply to remind people, even if at a much later oil change interval than is ideal for certain conditions is to simply CHANGE that oil in the first place.

        Honda has had an oil change monitor on the Accord since day one (1976), but those very early monitors simply went by how many miles driven from when it was reset, if it ever was after the oil was changed. This is simply based on what is determined to be a safe interval for MOST conditions, and oil available at that time.

        Most oils today, even conventional oils can go longer than the then typical 3000-3500 mile interval, but even there, I would not go much beyond 5-7K on older cars for a myriad of reasons, like I’d not go more than 9-10K on good synthetic in older cars for the contamination reason alone. This is especially true if your car has high miles, (150K and above) since at that point, the chances of wear are much greater than at lower mileage these days, given the same care is taken.

        And by older cars, cars that are 10 years, or older.

      • 0 avatar
        doctor olds

        @mawarms- “That raises an interesting question. If the computer in the car is calculating the oil change recommendation based on pre-set parameters such as conditions encountered while driving, and driving habits of the operator, then why would the product make any difference.”
        Bingo! In fact, the product does not make any difference. Oil changes are necessary due to contamination, not oil breakdown. Those snake oil salesmen are good.

        Oil level should be checked periodically as oil consumption is not directly related to oil life.

      • 0 avatar
        doctor olds

        @mswarms- I want to be clear in agreeing that synthetics are superior, they offer lower friction, have greater resistance to heat breakdown, and better viscosity control at a wider temperature range. My point is not that they aren’t better, but that they are better than vehicles that don’t specify them need, again because the reason to change is not oil break down with today’s oils, but contamination. I used synthetic in my Camaro for the track just to be safe.

        Doubling your oil change interval with oil that costs twice as much offers little or no savings,but substantial risk of high cost problems down the road. Ok, I’ll stop beating this dead horse!

  • avatar
    doctor olds

    @Zackman- Your usage supports particularly long change intervals since most of the time your engine is running it is fully warmed up. You can save some money by letting the oil life warning tell you when to change. If you want to be conservative, change it at 80-90% oil life.
    Can’t go wrong changing more frequently, but you may waste your money.

  • avatar
    28-Cars-Later

    Patrick

    I have the Pontiac equivalent to your Impala and I believe both W’s use the same transmission. I asked the transmission fluid question of my Aamco guy, he replied and I quote: “here [in Pittsburgh] you have extreme heat and extreme cold coupled with a very hilly landscape. If this were Ohio you could probably stick to 50,000 miles, but here I would drop the pan and change it every 25,000 or so”. I was changing mine at 55,000 shortly after I bought it.

    The other part of it that I ran into is the transmission fluid filter gets clogged/dirty just like any other fluid filter. I noticed the transmission fluid temperature (on the computer) would jump to 120+ degrees very quickly after startup. After my fluid/filter change on spring/winter/fall days it warms up slower than the actual engine temp, and never seems to get much higher than 116 (in local driving). I theorize it was jumping higher on start-up because fluid wasn’t circulating properly to properly cool the transmission.

    My two cents.


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