Ok, I never claimed to be a scientist or anything, but here is what I have noticed. I have in the past, taken synthetic oils like Amsoil, and Mobil 1 and taken them to a metal pan with high heat. The always withstand the heat well, barley beginning to bubble, and No smoke. However, I just took the Mobil 1 0w40 and did the same thing, and it bubbled pretty fast and started to smoke. I don't know if it is because it was on a gas stove this time and the others were electric, but I always heated the burners up before hand. I don't know if this means anything, but I just wonder if the Mobil 1 10w30 and 15w50 and the Amsoil 10w30 and 10w40 are better suited to deal with heat. I hope I am wrong, as I have Mobil 1 0w40 in my truck now.