I was at the dealership last night and asked about what weight oil they put in the TCH. Turns out they use the correct weight. I mentioned some of the experiences that people on this board have had and he incredulously said, "it states 0W-20 and 5W-20 right on the oil cap.

He also said that a customer came in with a Prius with the check hybrid system light on. They finally figured out that he had gone to a Jiffy Lube and they threw in the standard weight oil. Once they switched to the recommended grade the problem went away.

Heavier oil will take longer to build the presure after engine start and maybe that was the problem. I thought Prius was using 5w30 up until 2006, is 2007 selling already?

Not sure of the details. In fact, I'm not sure if he said Prius. I was just assuming that because the TCH is so new. But perhaps it was the TCH. His main point was that they always use Toyota recommended weights and there's a reason for their recommendation.

Your comment about the pressure after engine start sounds similar to what he was saying. He thought he also said it was in cold weather that the problem occurred.

Also keep in mind that the tighter tolerance newer engines need a thinner oil for proper lubrication at start-upand full operating temps.

It's what ralph said.

That's certainly true. However, if that were the main motivator of low weight oils, then all new Toyota engines would require it, not just the hybrid engines.

I would consider 0W20 and 5W20 thin oils. But, I wouldn't use 10W30 or 20W40 or 30W oils for today's engines unless specified. Remember the purple stuff they used to sell for high perf engines, I think it was 30W-50 or something like that?? A higher wt oil probably wouldn't matter for one oil change in warm weather but I wouldn't use it all the time.