Quote:
Originally Posted by DougR
Most of us agree that Toyota WS ATF should be changed no later than 100,000 miles under normal driving conditions. A few of us, myself included, prefer to drain and replace about 3.5 quarts rather than attempting to flush 14 quarts on a sealed transmission.
How often should one replace 3.5 quarts in order to maintain a mixture of low and high mileage fluid, such that average miles on the mixture does not ever exceed 100,000?
I created a spreadsheet to calculate it.
Change 3.5 quarts every 30,000 miles to maintain old-new mixture average fluid life under 100,000 miles. There will always be a small amount of the original WS fluid in the transmission, ~1 quart after 270,000 miles and ~1 pint after 350,000 miles.
I have these calculations in a spreadsheet. If you haven't changed fluid and want to know how to bring mixed fluid life down to a particular number of average miles, post your fluid change history and I'll calculate how many 3.5 quart changes are needed assuming a 14 quart total capacity.
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Hi Doug - thanks for the post. I realize it's been a couple years, but curious if you could share the formula for the partial fill / mileage? I have an 2018 with roughly 48.5k miles and thinking it might make more sense to use this method.
Thank you!!