Does anyone know who makes this oil for GM? I've heard it is Mobil, which would make sense with GM's obvious association with Mobil 1, but this was just a rumor that I heard. GM doesn't seem to go to the trouble of putting the GM logo on the synthetic, just the conventional. GM dealerships just stock Mobil 1 for their synthetic, but carry GM Goodwrench 5w30 conventional in bulk and in quart bottles.