I went to a new oil change facility with my truck and they offer only Mobil oils. The banner shows MC5000 up to the synthetic. I pull in and ask for Mobil Clean 5000 and the guys says it's 10.00 more for it and the Mobil Clean is what they have in bulk. After scratching my head, he agreed to give me the MC5000 for the regular oil change price. But why does Mobil offer a "lesser" grade of conventional oil? Pennzoil and all the others don't offer this "lesser" grade. Is the regular Mobil Clean on par with Pennzoil, Castrol, and Valvoline conventionals? Or is it that the Mobil Clean 5000 is a better oil than those I just mentioned?