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Discussion Starter · #1 ·
Wanted to see if I could string together a forum for people with Gen4s to post what maintenance they have been doing. Two things that have come up for me recently that I've been finding mixed reviews on are transmission fluid and coolant. Mazda claims trans fluid is "lifetime", although the consensus seems to be if you are obsessive and want your ride to run forever that you should change it. Same goes for coolant, service manual says 120,000 but people online recommend doing it earlier (some recommend every 3 years, even).

I'm curious if there are any other nuts out there with higher mileage than me that can shine some light on what they've done to date - and any insight on preventative/ obsessive maintenance overall is welcome. I would obviously like to do everything possible to keep it running as many miles as possible (so again, obsessive recs are welcome).

For the record, I have a 2019 approaching 30,000. Nothing crazy to date, have just been doing oil every 5k - and have done the low level stuff like filters and brake fluid.
 

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2021 Mazda3 Turbo Sedan
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I will preface my schedule with I work in drivetrain R&D, repair and tuning and live in what is considered a very hot extreme climate. I have a 21 Turbo sedan. I do oil changes around 5k with a high quality synthetic and factory filter. I changed the transfer case and rear diff fluid at 10k miles to get a baseline. Both fluids were in good shape with very trace amounts of normal break-in wear in the transfer case fluid. I will likely check it again in another 10k miles. The reason behind this is there is about 1/2 qt of fluid in both boxes and it does get used fairly hard, again with my severe climate the fluid heat cycles quickly. For the transmission fluid there is no such thing as a life time fluid. OEMs like to use that phrase, in the industry it is defined as for the life of the warranty, there is no legal definition. Mazda FZ fluid is a fantastic high quality fluid supplied by Idemitsu in North America but it gets worked hard in the Skyactiv transmission. I will be changing my fluid and filter at 30k miles. I base this on what we normally see in the pans of the Skyactivs when we service them, phenomenal transmissions but good fluid changes will only help them. Coolant I will change around 50k and brake fluid I will check with strips every 2 years and monitor the amount of moisture it absorbs.
 

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Discussion Starter · #4 ·
I will preface my schedule with I work in drivetrain R&D, repair and tuning and live in what is considered a very hot extreme climate. I have a 21 Turbo sedan. I do oil changes around 5k with a high quality synthetic and factory filter. I changed the transfer case and rear diff fluid at 10k miles to get a baseline. Both fluids were in good shape with very trace amounts of normal break-in wear in the transfer case fluid. I will likely check it again in another 10k miles. The reason behind this is there is about 1/2 qt of fluid in both boxes and it does get used fairly hard, again with my severe climate the fluid heat cycles quickly. For the transmission fluid there is no such thing as a life time fluid. OEMs like to use that phrase, in the industry it is defined as for the life of the warranty, there is no legal definition. Mazda FZ fluid is a fantastic high quality fluid supplied by Idemitsu in North America but it gets worked hard in the Skyactiv transmission. I will be changing my fluid and filter at 30k miles. I base this on what we normally see in the pans of the Skyactivs when we service them, phenomenal transmissions but good fluid changes will only help them. Coolant I will change around 50k and brake fluid I will check with strips every 2 years and monitor the amount of moisture it absorbs.
Appreciate the response! Transmission fluid is really the big one I have been contemplating as I approach 30,000 (currently at 29,000). Consensus seems to be change the transmission fluid/ filter regardless of the "lifetime fluid" badge, but I wanted to make sure I wasn't jumping the gun on it at 30,000. I guess that is what I will do next. Otherwise, I've done a similar track so far - oil changes, brake fluid, filters, etc.

Trans fluid and coolant were really the two items I wanted to pick people's brains on, so I genuinely appreciate the response(s).
 
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