Oh, the great debate.
I can see multiple sides of the argument:
- How many of these motors have failed due to 10k oil changes? I haven't heard of any. But then again, there are people who run them low on oil, and technically, with Toyota specs, the motor can burn 1qt per 1k miles. That's 10qts of oil (or nearly 2 oil changes) within 10k miles. Does everyone who runs their motors at the full intervals check their oil level? When I took my 4R in for the 5k service, I don't think they even popped the hood to check levels.
-10k oil change intervals and free services look great for Toyota. They advertise it everywhere. If they can get by spending half as much (changing the oil every other service instead of every 5k) they are saving a lot of money!
-10k oil changes make Toyota seem like a much more environmentally friendly company. Their vehicles require less frequent oil changes, thus they are kinder to the environment and create less waste.
-Salesmen love to say "just bring it in for service once a year!". Normal customers like to hear that. They don't want to keep track of miles and only want to go to the dealer for services when they absolutely have to. That's why they bought a Toyota!
-Oil is getting better. Our motors have good overall engine cooling (coolant temps maintained in the 190s) and we have stock oil cooling as well. 5k+ oil change intervals have been the norm for manufacturers since the 80s. Even on old, regular oil. Hell, my CRF250L has a 8k oil change interval and it holds less than 2qts of oil! My aircooled BMW has a 6k oil change interval though, so oil temperature control is key.
Toyota had an issue with sludging years ago. That was mainly due to using regular oil, bad oil galley design and customers continuing to go above and beyond extended oil change intervals. Toyota wasn't the only one, VW/Audi and others had the same issue. The switch to quality synthetic oils changed that, but oil levels still need to be checked. Hence the move to electronic dipsticks.
It pretty much gets down to, do what you want. Change it early or don't. Even at 10k, that's relatively conservative for a motor which holds 6.5qts of oil and has good filtration. The only think I don't like about Toyota's setup is it only considers mileage, nothing else, so it must be a fairly conservative number for them to use it. Many manufacturers factor in items such as fuel used, number of starts, average coolant and oil temperatures, throttle positions, etc to get a good read on how the motor is being used. My previous BMW 525i would get up about 16k miles before it'd recommend an oil change!
Point being, if you were in the market for a used 4R and found one which was dealer serviced, 50k miles and the oil had been changed at the recommended 10k intervals, would that scare you off?