Auto transmission fluid

How often should you change your auto transmission fluid?

In the glovebox of your Lexus, hopefully, there is an Owners Manual. Enlighten yourself! Turn to the section on “Maintenance”

This is one area where I don’t go by the owner’s manual, because I have one vehicle where changing ATF is not mentioned, and the fluid (Dexron III) is not really a lifetime spec. Suggest every 25-30K miles pan drop, filter change and fluid change out.

As mentioned, the proper time or mileage interval will be in your owner’s manual. In addition, most manuals also have a “severe service”, such as trailer towing interval, which is a lot shorter.

Every 25-30k miles on an automatic regardless of what your owners manual says.


Outside of reading your owner’s manual and seeing what is recommended, which is really a minimum recommendation, this is one of those personal opinion issues. Some say drop the pan and change the filter, which only works on cars which actually have filters.

Others say pay the exorbitant price to have them suck it out the fill/measure tube, and put in new fluid.

A few have a plan which disconnects the transmission from the cooler, and runs the car until it runs clean, or something like that.

Several years ago, a man with a new luxury car asked Tom and Ray if they thought it would be okay to drain the 3 quarts or so of ATF every time he changed motor oil, and add back that amount. They said it was fine.

That is what I do, not every time I change oil, but maybe every 10,000 or 15,000 miles, and I changed to synthetic ATF. But, my Sienna only has 164,000 miles, so who knows what the future holds?

In my opinion, any of the three which might “trip your trigger” (as my daughter says) is far better than the average car gets, and is an acceptable choice.

As the old saying goes, you pays your money and you names your poison.

Advocates of each method report very long transmission life with their method.

There might be an exception to what I have written. I have seen reports that the Honda Odyessey is sensitive to both type of ATF and maintenance cycle. Read your owner’s manual, and if it specifies a certain brand of ATF, why not? It is not something you have to do every day.