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Your comments make perfect sense. As you say, all cars have failures, and some models have way more than others despite the manufacturer's reputation. My experience with transmission fluid changes has not been good. It's common sense that clean(er) fluid is better, and it's cheap preventive maintenance. It just hasn't made any difference in my case. Depending on the model, when it's time for them to fail, they fail. True story. Years ago I took my station wagon to a local garage for a transmission fluid change. When it was done, the manager called me up and said "I have good news and bad news. The good news is the transmission fluid is changed. The bad news is your car is totaled!" I said "WHAT?" A woman was driving past the garage on the way to pick up her welfare check. Just then her engine died so she lost power brakes and power steering. The garage is on a bend, so she went straight into the garage parking lot and plowed into my car, totaling it. Worse, my car plowed into the car beside it.

Lenore, that is interesting. What is your guarantee based on? I've had a Chrysler van and Honda van, both of which had the transmission fluid changed per mfg's rec and both had transmission failure anyway at about 70k miles. My daughter has a Toyota van that never had the transmission fluid changed, and it has over 250k miles without a problem. High heat will cause the fluid to deteriorate in a remarkably short period of time, perhaps a few thousand miles. So if the transmission gets hot, it can fail even if the fluid was recently replaced. My Lexus has a transmission cooler, I've followed the mfg recs, and not had a problem at 70k yet. My new Honda van also has a transmission fluid cooler. Do you know of any vehicle (especially a Toyota product) with a transmission cooler installed that has had a transmission failure when the mfg recs were followed?

Transmission fluid deteriorates exponentially with heat. Fortunately the RX-350 has a transmission fluid cooler which keeps the temperature down. Unless you tow up hills on very hot days, you probably never have to change it. Terry, I completely understand your desire to spend some money to insure that your vehicle is reliable, especially if you bought it used. However, some vehicles, like the RX-350 are so well built that if you follow the basic maintenance schedule (primarily engine oil change, filter changes, etc.), check fluid levels (including transaxle occasionally), and pass inspection, you really don't have anything to worry about.

Transmission fluid deteriorates exponentially with heat. Fortunately the RX-350 has a transmission fluid cooler which keeps the temperature down. Unless you tow up hills, you probably never have to change it. Brake fluid absorbs moisture. It's a function of time, not mileage. If you don't change it, you run the risk of expensive brake maintenance due to rust of calipers, etc. I have it replaced every 3 years for preventive maintenance.