I've been Using M1 oils in 12 to 15 month fairly low mile oil changes in the same rebuilt engine for the last 11 years. I have used in this general order: M1 10w-40HM first 4 years M1 TDT 5w-40 M1 10w-40HM M1 0w-40 FS SN M1 0w-30AFE M1 0w-40 SN Couple M1 0w-40 back to backs in there. I've had undesirable valvetrain noise for the last 11 years. The first batch of 0w-40 attenuated it to a large degree, but it returned half way through OCI, and stayed the same through 0w-30AFE and the last 2 batches of 0w-40 I recently stood in Wally world, Looking at another M1 0w-40 5 Qt jug for $22.88. I saw Pennzoil Platinum 5w-30 and 10w-30 for the same price as the M1 5 or 10, 5 or 10. Heckwith it, Unlikely to see below freezing temps this year, but might drive X country twice. Walked out with PP 10w-30. I let the M1 0w-40 drain out for several hours. Prefilled a new XG-8A. Once I strarted it I heard the same valvetrain noise I have been listening to for the last 11 years and just learned to live with. But then this infernal valvetrain type of noise started lessening with every passing second, and now I can barely hear it. I did not drive it to full temp, but today I did, excpecting the noise to return. Still super Quiet. I like Quiet. I am rather surprised at just how much quieter it is. I frankly do not believe it. Not much Info on PP 10w-30 out there. No Voa's, Nothing on PQIA. Anybody know the TBN or the make up of the add pack or care to guess what they are using in this GTL synthetic? Glad I got off the M1 train.