Originally Posted by 02SE
As to the guy that mentioned the 1MZ-FE being sludge monsters, I was working at a Toyota dealer when they came out. The BIG issue was that people bought or more often leased vehicles due to the sterling reputation for reliability Toyota had/has, and then people NEVER changed the oil. I'd see cars come in at 30-40k miles, with the original factory fill, because the engine was making a "funny noise". Invariably the goop that used to be oil, was no longer able to do it's job...
I know that the sludge problem was mostly due to a lack of proper maintenance. Some people think that Toyotas are indestructible and don't need regular maintenance, in particular, some of the people I have known that trade them every 2 or 3 years or lease them.
I had a 98 Camry V/6 and changed the oil every 5k miles using Mobil 1 exclusively. I also check my fluid levels and tire pressures at least once a month. When I got rid of the car it had 220k miles on it and never developed an ounce of sludge buildup.
Toyota can certainly take part of the blame on this one though. During that era they went to a 7500 mile oil change interval recommendation. This could be problematic (and was) when using cheaper conventional motor oils combined with certain types of driving, and letting the engine run low on oil for a couple thousand miles during each oil change cycle exasperated the problem. Because of this, the 1MZ-FE wasn't the only Toyota engine that exhibited a sludge buildup problem, just the most severe. Also, you didn't see the problem as much in Lexus products with the 1MZ-FE because of the fact that most Lexus dealers were selling/using synthetic oil in their service departments.