M1 is not true synthetic. at most it is 90%, and some grades are actually less than 20%.
that being said i would pick PP-5W30 over M1-5W30, as i have seen quite a few used oil analysis' done on both and the PP turns up better results.
and no im not saying i recommend it, its just that i dont DISLIKE it as much as M1 5W30.
Alusil, Dinan DME | ITG Air Filter | Eibach/Bilstein HD | 26/20 Swaybars | Iridium plugs | Depo/ProLumen HID | Optima batt. | no AC | Stoptech brake lines, Frozen rotors, brass bushings, Superblue