Piston Slap: The Truth About "Good for Life" Fluids?

Sajeev Mehta
by Sajeev Mehta

TTAC Commentator Dror writes:

I own a 2006 Mazda 3, hatch 2.3 liter 5 speed A/T. I bought the car new, I have 45k miles now, car drives very well and I tend to follow maintenance schedule as the book suggest. My concern is that there is no schedule for A/T fluid change, what does it mean? Don’t ever change it, or let the dealer decide for you?

If it’s up to the dealer, I’d spend ridiculous amount of money on stupid things like “the 30k service” that is known to car dealers only, but they never suggest anything like that when drop by every 3 months/3k miles for oil. I live in NYC and that car spend significant time of it’s life on Manhattan streets: I would like to know if anyone knows the answer, I really don’t like to mess with my A/T if I don’t need to.

Sajeev replies:

Never let the dealer decide: though these guys seem honest, I once saw a Dodge dealer convince a friend to perform differential fluid changes every 15k miles. I told her to stop it, but you can only lead a horse to water. Whatever.

Now, you live in NYC (i.e., stop-and-go traffic) and have more than an occasional heat wave. Both items are bad news for transmission fluid. I’d change the fluid on a regular basis: sealed for life transmissions are a gimmick, a joke that should (fingers crossed) pass as short term leasing and easy credit gets harder to find. So do not RTFM, because you love your car. Or hate it and have no alternative. Or want to pass good karma to the next owner: it’s all good.

If you really love your car, get an external transmission cooler for maximum fluid life. But even I think that’s overkill in this application.

[Send your queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • Daniel J. Stern Daniel J. Stern on Sep 08, 2009

    However often you choose to change the fluid, make certain to use the correct fluid, and only the correct fluid. Not only are the usual con artists (Scamsoil, et al.) on hand to babble about their one be-all-do-all-replace-all fluid (at $OMFG/quart, natch), but there are also additives on the market claiming to "convert" Dexron into various other fluids. Fact is, there's no such conversion possible. Modern automatics are a great deal more sensitive to just about every characteristic and performance aspect of transmission fluid; "close enough" isn't. For many years, Dexron was the de facto universal auto trans fluid, used in just about everyone's automatics with the exception of some Fords and a few imports nobody drove. That's no longer the case. Use whatever kind of fluid your car's manufacturer specifies, unless and until it is officially superseded by another fluid, at which time use the newly-specified fluid.

  • Ddr7 Ddr7 on Sep 08, 2009

    Thank you all for your comments, I guess I do need to replace the fluid, just for fun, I would call Mazda to ask why it's not in the car manual, the car is still under warranty, so why not? dror

  • Lurlene Lurlene on Sep 08, 2009

    I have a good deal of experience with this exact car/transmission. It is VERY HARD on transmission fluid. Granted, mine is being driven in Texas where it is rather hot... Within the first 20k miles, the fluid had turned from that nice clear out of the bottle red color to a brown-ish murky color. I drained via the drainplug and refilled with ~3 quarts of Mobil 1 ATF. Drained and refilled with another 3 quarts at the next change interval. Ever since, I've been draining and refilling every 3-4 oil changes, or whenever it takes on a brown-ish cast. I would suggest you go for just a drain/refill with a high quality fluid every 20-30k, and skip the full system flushes.

  • Golden2husky Golden2husky on Sep 08, 2009
    A lot depends on duty cycle.... A truer statement has never been made. So many people think that mileage alone is what is important. A vehicle that is driven on a (mostly) daily basis and logs 3500 miles a year is going to have an extremely high rate of wear at 25,000 miles. A "garage Queen" is a different story. I put less than 70K on one of my cars in 14 years, and the car was never used as a commuter or on a daily basis. It does go for spirited drives, and for the occasional road trip (would love to hit the tail of the dragon). As long as the sitting period is not too long, atrophy is not an issue. The car looks like it is three years old...