I was a big M1 guy and always praised it's virtues but I tried a conventional Dino(Exxon Superflo)for 1500 miles and was intially happy but I had a change of heart and went back to M1. I was always happy with the M1 in my other cars and I used it in this particular car(99 Corolla)since it was new.The engine was always spotless and the oil came out in good shape visually. The Exxon darkened after 1400 miles(I know this is not an indicator of anything)and seemed to leave some brownish residue in the engine.Never had this happen with the M1.Never became 100% clean by wiping the exsposed internal parts with just the rag.Sure it looked cleaner after the wipe but you could tell brown oil had been there,kinda stained I mean. Went back to M1 and after a 100 miles or so I am back to spotless and looking fresh from the factory.I guess I didn't appreciate the M1 as much untill it wasn't in there.Maybe I'm too anal but most likely if you are reading this it wouldn't come as surpise if you found this important too! Well anyways long live M1 and long intervals!It's also the only oil I trust that is WIDELY available every where pretty much that will do a great job in my 02 Sienna for 5K while leaving the internals sludge free. Now for the Schaeffers.This is really only about the Nuetra 131 as it's the only Schaeffers product I have experience with but man this stuff is good!Working good to desludge both an extreme case of sludge(99 Hyundai Elantra)and a more minor case of sludge(79 BMW).Go Schaeffers!