Whats the main difference other than Price? After I finish up the 3000 miles on the Pennzoil HM in my truck I'm going to synthetic. Is this a bad idea at 121,000 miles? No leaks on my truck (2005 Ranger) I just use HM oils for that reason, I own a HM truck. I've mainly used QS Products in my truck (QSGB, QSHM) and I think I like the way my truck runs on them vs this Penn HM I put in a week ago. Seems as if the Penn has made my truck less sensitive and I have to take more time to accelerate. Regardless, is Ultimate Durability a good oil? I never hear about it on here much, I do hear about PP quite a bit. Also, after reading alot on here about oils, Im thinking of putting 5w-20 in my truck for the first time since I owned it (Ford, Local Auto Shop, and Goodyear all put in 10w30 as did I for roughly 20-30k miles now) would this be a problem now that ive run 10w30 on it for so long? the manual and ford both say 5w20, idk why the local ford dealer (I had free OCs for a year after I bought the truck) put it in to begin with