Piston Slap: Burning the Midnight Oil in the Outback
Jeff writes:
Long-time lurker here with a question: I’m currently driving a 1996 Outback with 162,000+ miles. Over the years I’ve had to make a few minor repairs in addition to regular maintenance, but nothing more serious than replacing an alternator. The car still drives well and gets 23-25 mpg in daily mixed driving (and about 28-30 highway), but has been slowly using extra engine oil for about the last 40,000 miles. I make sure I check the oil level at least bi-weekly, but normally don’t have to add any for at about 2-3 months, or after an extended highway drive. (75-80 mph turns the engine at 3000+ rpm; there’s a definite drop in the oil level during the trip.) I’m using full synthetic 5W-30 as recommended by the manual.
The questions: what’s going on in the engine that could cause the oil leak/burning? Is a repair (or even ignoring the problem) economical enough that I can get a few more years out of the car, or should I bite the (financial) bullet and trade the old workhorse in? I can certainly afford to buy a new Subaru, but I’ve spent the last 14 years wearing a comfortable groove into the driver’s seat. Thoughts, opinions, flames?
Sajeev Answers:
Unlike our last Piston Slap regarding Subies and upsetting levels of oil consumption, this one is about age. Though it’s kinda shameful that a modern car with 162k on the clock burns that much oil, there are some basic things to check. And not all of it means you need a new set of piston rings, a new motor, or a new car.
- Simply look underneath the damn thing and make sure you don’t have an oil leak. Fix the leak and you’ll fix the problem.
- According to the Internet, the original Outback was not turbocharged, but if it was, old turbos can burn oil before they ultimately fail. New or low mileage used turbos are never a bad idea in lieu of a new car payment.
- Condition of the PCV (positive crankcase ventilation) system, because a blocked PCV valve can lead to significant oil burning on a worn motor. Though not especially legal, you can install a breather valve in lieu of an oil filler cap to “relieve” the system of its oil burning properties.
- In that vein, we’re talking about excessive engine blow b y from worn “oil control” piston rings. There are several ways to check, but a wise move might be to consult a Subaru forum about your choice of engine oil, as this thread elucidates.
- While your fuel economy implies otherwise, this might be a good time to do a compression check on all cylinders to see how healthy your “compression” rings are in the motor. If all else fails, junkyard motors are cheap, come with a warranty, and most shops can install them with a day’s worth of labor.
No matter what, I’d reserve judgment on the Outback until we shine more light on the problem.
Send your queries to mehta@ttac.com
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Hi everybody. I appreciate the feedback and the suggestions. Based on what I've read here, and at the Bob the Oil Guy and the Outback forums my plan of attack is: 1) Have a compression test done. 2) Switch to non-synthetic 5W-30 at my next oil change. (Sorry about the confusion caused by the original post; I meant to say Subaru recommends 5W-30 and that I'm using a synthetic of that weight.) Based on consumption and performance after that I'll see about switching to 10W. 3) Get a couple bottles of Auto-Rx and perform the engine cleaning ritual. As always, I appreciate any constructive comments on the above, although well-crafted flames always fun to read. A little more background on the Outback itself: it was bought in 1996 at Schuman Carriage in Honolulu to replace my wife's Sundance. (Long story on that; short version is: Not my fault.) I's got the 2.5L engine with the 4-speed automatic; all maintenance has been conducted in accordance with owner's manual. It's a military brat; it's literally dragged me and the family across the country a half-dozen times and performed wonderfully as a short commuter in between moves. It currently lives in southeast AZ and is being eyed for inheritance by my 16-year old son.
Slap a used motor in there if the rest of the car is in good shape. The way I look at it- if you drop 2 grand fixing it...that's about 4 or 5 new car payments. Back in 98 we overhauled the engine on our 90 Legacy with 170 k on it and got another 3 years out of the car before replacing the car. Replaced it with a 2001 Outback that has 200k on it that had the same thing done to it 2 years ago. Our daughter uses it at college....perfect car for parking in downtown Philly...it looks beat to hell but it runs like a top.