Exactly! . My wifes 300c with a 5.7 hemi even manual says NO synthetic and 5w30 0r 5w20 and it has 94,000, Never uses oil and has no valve train noise what so ever. Even says 87 octane only. Car never misses a beat and runs awesome. Now my 2500 6.4 gets 89 octane, PPP 0w40 every 5k and it has...