Hi MG, I don't disagree, but consider that many high performance cars and longer drains must account for fuel dilution. I'm not saying thinner is better. Not at all. But for 99% of most drivers here in the US, that never go above 85mph, a 5w-20 (which btw are all group III and group II+ now) are absolutely fine. CAFE is the reason, no doubt. BUT, you can make an oil of lesser viscosity perform very well if need be and that is what has happend. Honda would not put it's reputation on the line of 20wt oils would cause engine failures. That is my opinion. Would I race with a 5w-20? Not unless it was Redline or FUCHS. To complicate matters, not only are oils getting more thin, they are reducing the amount of GF-4 as your well aware of.