Service guide for 2012 ES 350 Lexus says not change of transmission fluid is required for life of car. Is this true? If not, when should you change? Car has 66,000 miles.
"Lifetime" is ambiguous. On a sticker on the transmission fluid dipstick of my 2010 Toyota Rav4, it states that the fluid is lifetime fluid and doesn't need to be touched. However, upon closer inspection of the maintenance guide, there is a directive to replace the transmission fluid at 120,000 miles.
If you plan to keep your vehicle for quite a while, I would replace the transmission fluid when the maintenance guide states to, or if no interval is stated, at 120,000 miles. It does not need to be flushed, just drained and replaced. Many Toyota/Lexus vehicles are sensitive to the amount of fluid in the system. My local dealership says to replace the fluid every 50,000 miles after the first 120,000 mile service.
I did the change when my car hit 100,000 miles, and though there was little noticeable difference in the performance of the vehicle afterwards, the fluid was quite dirty and less viscous than the new fluid when it came out. As long as you replace the fluid with the same amount that came out, you should be okay. Also, if your car is equipped with one, replace the transmission fluid oil filter. Mine did not, but some models do.
Mercedes-Benz said the same thing about 15 years ago. Many owners suffered transmission problems as a result.
Change the trans. fluid (ATF) every 30k miles. Since you typically only replace half the fluid during a change, however, have the service performed three times in a row -- allowing a month between changes -- to fully clean the transmission.
If you'd like to save money after the first change (with filter/screen replacement), you can pump the fluid out of the dipstick yourself. I use this pump available on Amazon.