One thing I've wondered about is why all these car companies are going to 20 weight oils. I have no doubt a 0w20 can lubricate an engine greatly, but what's the reasoning behind it? For example, the Chevy Silverado has always been specced for a 5w30, and now they're calling for a 0w20. Is it tighter engine tolerances or CAFE standards for fuel economy? Same with Toyota Camry's, once were calling for 5w30, now they call for 20 weights. Another question I've wondered: if you got 2 cars that called for 0w20 and ran them in the same exact environments, miles, and all factors were the same for say, 300,000 miles. One of them was run on a 20 weight and another on a 30 weight, would there be any differences in engine wear? I've never had a car yet that called for a 20 weight, and with 5w40 in my TDI, I have no experience with 0w20 and have always been curious. Thanks.