With these engines today, and the synthetic's, I think it's safe to say if you never change your oil you can get 100k miles before it slowly dies. I trust the toyota engine manufactures when they claim 10k oil changes using synthetics are all thats needed....of course thats for normal use driving a lot of highway miles per day. Even when I was in Europe a few years ago they have even longer oil change intervals, and all their cars have been doing fine. I've only had 10k mile oil changes on our 2012 prius with the same 0w20 synthetics my tacoma needs. The prius is at nearly 115k miles, still runs like new. I spoke with the tech that changes the oil, says with the same oci's, he's got prius's with over 250k miles out there running fine. I'll bet the rest of the vehicle will fall apart before the engine does.