I don't have a Hemi owners manual, but I do have a 1972 Plymouth Road Runner owners manual. For the 440 at 32+ degrees 10w-30, 10w-40, 20w-40, 20w-50, 30 are all acceptable. For maximum performance driving 20w-40, 20w-50, 30, 40 with Mopar High Performance Sulferized Ester #3683842. I use Valvoline VR-1 Racing 20w-50 conventional. The engine is original with low miles and not rebuilt. If it was rebuilt, I would use the same oil in synthetic, or what the rebuilder recommended if he had a specific choice. Both VR-1 oils have plenty of zinc and phosphorous for flat tappet engines.I still don't have an owners manual for my recently acquired 1968 Charger 426 Hemi. Stock all original engine. What is the reccomended oil viscosity? I'm seeing many people saying 10-40, 15-40, 20-50. What does the manual say?
Yes I will be running a Zinc oil.
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