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Must 5W-20 be Used in HEMI MDS Engines?
Is 5W-20 still the choice grade for 5.7 HEMI MDS engines under extreme temperatures? The Owner's Manual and related TSBs all state that 5W-20 must be used whereas pre-MDS HEMIs were recommending 5W-30 and even 10W-30 for hot climates. Does 5W-20 still provide optimum protection in severe conditions above 100°?
-- Emiliano Arzate, Topeka, KS
We recommend you follow the recommendation in your vehicle's owner's manual. If you are concerned about durability due to higher temperatures, then going to a higher viscosity grade would provide a better oil film under high temperature conditions. You might also consider using Mobil 1 5W-20 fully synthetic motor oil, which will provide 5W-20 viscometrics but also provide a performance upgrade at the same time.