This post is a bit dated in information, but I felt I owed it to BITOG to share it as the group influenced my choice of PCMO. Having worked for Mobil, I was a die-hard Mobil 1 user for years. Until Shell bought Pennzoil and came out with GTL Ultra Platinum motor oil. BITOGers posted excellent reviews, UOA's, etc., and Shell's advertising with the cleanliness over M1 didn't hurt either. So I changed to PUP and have been with it ever since. Here's what I noticed - my OCI's were fairly regular before I retired...3x per year on all vehicles @ 6k miles, except RV which averaged 3k miles per summer. The vehicles OEM Manual specs different SAE vis for each vehicle, which I stick with. - oil consumption averaged app. 1 quart per OCI (@ 6k) on M1 per passenger vehicle. after change to PUP, there is no noticeable oil consumption on the dipsticks - on any vehicle. - oil consumption on the RV averaged 1 quart per OCI (@ 3k) on M1. after change to PUP, there is no noticeable oil consumption on the dipstick. - 1st oil changes with PUP had noticeably darker oil drains. I don't have UOA to prove whether this is advantageous or not, but I would think so? Neither do I know why since I don't know the base stock recipes. I suspect PUP has a better base oil with lower NOACK and better DD additive package. If the rings and grooves are cleaner, the pistons are sealing better (less sticking)? Again, this is educated speculation based on what little is known about these oils. Since PUP was first introduced, Mobil responded with "EP", but I haven't tried it. I've been pleased enough with PUP's performance and availability (now days) to not experiment further. The new GDI engines have me wondering what is optimal, though. I have one of these now, and surely more on the way.