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2004 Mazda 3 Transmission Fluid never been changed

We are having a debate about whether to change the Transmission fluid of our car. Has 114,000 miles. Runs great. Our mechanic has been researching whether to change transmission fluid or not. Manual says to inspect but nothing about changing it. It has NEVER been changed and no problems with transmission. Online some say it should be changed every 30k and some say to never change it. Some say if car has over 100K miles that changing it will create slippage in transmission and problems will start. I’d like to hear some expert advice as we don’t want to create problems and expense where there is none. We regularly maintain it and change oil every 3 months.
Thank you!

Auto trans fluid should be changed every 30k miles no matter what the factory recommendation is.
Not changing the fluid is a factory PR recommendation, along with others, to make it appear their vehicles need little maintenance. Most make it out of the warranty period…

Changing the fluid will not hurt it. What often happens in the cases where problems develop is that someone will change the fluid on a neglected transmission, suffer problems immediately or maybe 6 months later, and blame it on the fluid change instead of the fact that the trans had been neglected.

+1 for ok4450. I think the automobile manufacturers who have transmissions with “lifetime fluids” will one day face class action lawsuits or customers who will not buy their vehicles or both.

@JudyD what does the owner’s manual say?
I’m surprised your mechanic doesn’t want to do a filter and fluid service.
Ask your mechanic to service it now.

Look on page 10-4. It tells you what ATF to use. Section 8 has the maintenance schedules. It doesn’t have an interval for ATF service. Nevertheless, I would do it now.

Changing the fluid will not cause the transmission to slip, unless you use the wrong fluid. I would not flush the transmission. If the fluid is a nice pink or red color, not brown(ish) and you have a drain plug in the pan, I would simply drain and refill with the specified ATF. This on exchanges about half of the fluid, but that is enough to renew the additives needed to extend the life of the transmission.

If the fluid is brown(ish) or black(ish), then have your mechanic drop the pan and clean or replace the filter, clean out the pan and then refill. Check the color a week later and if it is still discolored, drain and refill again.

Transmission filters are replaced, not cleaned.

Thank you all! It is wonderful to hear 4 opinions that agree! We are going to drop pan, clean and refill. You all have made my day.

My Mazda 3 SkyActiv transmission has a sealed case, no dipstick, and a highly specialized synthetic transmission fluid. Mazda warns not to open the case or the warranty will be voided. When I get to 120,000 miles I may check back with Mazda again but, when queried directly after my purchase, I was advised not to have anyone open the case or attempt to change the fluid. Interesting…

For those who argue that, once you have gone for many miles/years without changing transmission fluid, it is dangerous to change it, I ask…

If you have gone for 20 years without having a Colonoscopy or other recommended medical procedure performed, does that mean that you should never have that procedure done?

Asking that question usually allows people to see the faulty reasoning behind the “don’t touch the transmission fluid” philosophy.

Time after time we see the same thing.  Someone puts off changing the transmission fluid (this is aggravate buy the fact the dealers and manufacturers, figure that if something goes bad after 50 or 60,000 miles you will just buy a new car and they will profit.  this is supported by all the people who don't change their auto transmission and they blame the car, when most of the time simply doing some reasonable maintenance, they could have avoided the whole problem.

@JosephEMeehan At 50,000 to 60,000 miles nearly all owners have stopped visiting the dealer. Most dealers barely know how to do transmission work. And you are right, the transmission usually does the car in at a higher mileage.

A friend had a Mazda 626 and at 100,00 miles or so, when he car was 12 years old the transmission packed it in, totalling the car. The rest of the car was immaculate and the engine near new. He now has a Honda Accord and a Honda Odessey, and has taken my advice to drain and fill the transmission with HONDA fluid every 30,000 miles to avoid the same problem.

[I deleted my comment/question in this space after I realized I was inappropriately hijacking this thread. I can re-post it later on a new topic.]

New fluid will only help save the transmission, a flush is not recommended over conventional change of fluid and filter. Old fluid is not better for a trans than new fluid.

I looked up the service schedule for your vehicle. And Mazda recommends that the transmission fluid be serviced every 30,000 miles. So it’s way overdue.


Tester: Where did you find that?

I just looked at the scheduled maintenance in the owner’s manual for that car on the Mazda USA site (, and I could not find any reference to changing the automatic transmission fluid.

It wouldn’t be the first time I missed something.

@bloodkyknuckles your car is newer and has a different transmission.
The OP’s car has an automatic with an easy to service transmission. It has on old school pan and filter.

I looked it up on my Mitchell On Demand on line vehicle repair subscription.


Thanks Tester. It’s interesting that Mitchell lists maintenance schedule information that appears to not come from the vehicle manufacturer.

I have mine done every 20k or so. My vehicle is approaching 190,000 miles with no trans issues. It’s pretty much basic maintenance like oil changes.


@Tester. I have had Haynes and other manuals over the years. The “maintenance recommended” is often a combination of the factory and what the writers know as “practical experience”, and often goes beyond the factory specs.