the 6.2 absolutely 100% does not REQUIRE 91 octane; it'll adjust timing to prevent engine damage
per the owners manual
Recommended Fuel (6.2LV8 Engine)Premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating (R+M)/2 of 91 or greater is recommended. If unavailable, unleaded gasoline with a posted octane rating of Driving and Operating 30587 may be used, but will result in reduced performance and drive ability. If heavy knocking is heard when using gasoline rated at 91 or greater, the engine needs service. Do not use any fuel labeled E85 or FlexFuel. Do not use gasoline with ethanol levels greater than 15% by volume.
octane rating is a measure of fuels resistance to detonation (not energy or cleanness or anything else)
if you run less then 91, under load it'll start to knock so the truck will adjust timing which lessons performance but saves the engine
does 91 vs 87 improve mileage; maybe, empty on a cool day, nope; hot day towing, perhaps
does 87 vs 91 hurt the 6.2; no
per the owners manual
Recommended Fuel (6.2LV8 Engine)Premium unleaded gasoline meeting ASTM specification D4814 with a posted octane rating (R+M)/2 of 91 or greater is recommended. If unavailable, unleaded gasoline with a posted octane rating of Driving and Operating 30587 may be used, but will result in reduced performance and drive ability. If heavy knocking is heard when using gasoline rated at 91 or greater, the engine needs service. Do not use any fuel labeled E85 or FlexFuel. Do not use gasoline with ethanol levels greater than 15% by volume.
octane rating is a measure of fuels resistance to detonation (not energy or cleanness or anything else)
if you run less then 91, under load it'll start to knock so the truck will adjust timing which lessons performance but saves the engine
does 91 vs 87 improve mileage; maybe, empty on a cool day, nope; hot day towing, perhaps
does 87 vs 91 hurt the 6.2; no