I do not like maybe statments. So in the owner's manual for my new 2011 Durango with the 5.7 Hemi it states that it is recommended to use 89 octanie fuel, but then says 87 is ok. So which is it? I know that higher octanes will make the engine run better, will you get better mileage? Less issues with ingition. If you use 87 and then have an engine issue, would using the lower octane void the engine warranty?
I would run the higher octane. It will run the lower octane but if your engine gets under strain it could cause some spark knock. The pcm will cut the timing back to eliminate it but if it happens a lot it's not good for your engine.