Originally Posted By: bourne
@weebl : Here's a thought ....... progress. Every company I know who manufactures something is always working on a new product. Maybe when Toyota came out with the engine 5w30 weight was probably the thinnest they could go while still maintaining the level of protection/wear that they would like to see out of the tire. But as time passed by 5w20/0w20 weights were introduced in the market. Some more time passed by, the companies improved the quality of their oil to meet the manufacturer's demands.
Toyota then tests they new 5w20/0w20 weight in their older engines and comes to the conclusion that they provide acceptable wear requirements ( might even be better, its anyone's guess ). I do know that car manufacturers do not backspec oil unless they know for sure that it will not adversely affect the engine. That would be like a doctor telling his patient to try a new medicine because its worse than the one he's using already.
Quite possible. But how do any of us know how Toyota arrived at the xW-20 recommendation? I know an xw-30 will work well in the application. In fact, I've used xW-30 in the majority of applications over the years. If I had a way to know for sure xw-20 protects as well in this application, or, I have operating conditions that warrant the viscosity of xw-20 over xw-30, then I would make the switch. As it is, I am constantly tempted by the Toyota 0W-20 given it's great price and the fact it is a great oil.
As for viscosities in that engine, I'm pretty sure I can use anything from an xw-20 through an xw-50, and it wouldn't explode or anything like that, given that a wide range of tolerances are often inherent in the design. That said, because it is tolerant of something, doesn't mean it is ideal for a given circumstance. If I had to, I could tolerate eating tofu and brussel sprouts, but I don't like them, so I don't.
Now, if I buy a new vehicle that specs xw-20, then that is what I will use for it.
