This seems to be a growing issue. Toyota recommends 0W20 or 5W20 and the dealerships want to put in 5W30 and then treat you like you're an idiot if you suggest using Toyota's recommended viscosity. I'm guessing it's because they purchase the 5W30 relatively inexpensively in bulk and don't want to buy the other weights.

I looked under my hood yesterday. On the fuel filler cap it lists 0W20 and 5W20 as the recommended viscosity. I'd guess that 5W30 won't hurt anything except mileage, but I don't want to bet my engine on it, especially since it's effect will probably not show up until after the warranty is history.

I hit 3800 miles this morning, so I've got a month to figure out what to do during my first oil change. I think I'll give their service department a call and find out what they use.