as with any engine, the DESIGN of the components...meaning...Comp ratio, cam selection, ignition timing and even the material types used all can have an effect of what octane is NEEDED, the 5.3 is designed around the lower octanes...until you introduce HIGH HEAT TEMPS, that is when GM recommends the use of higher octanes. the 6.2 is already a higher compression and therefore by design, GM recommends the premium levels of 91 or higher.
an engine only NEEDS the octane it NEEDS, higher octanes dont always make more power....that is not what octane ratings are for.
i can say i have tried all octanes just to see, i have never done this is high heat temps, nor during a loaded down drive....what i have noticed mostly, is the mileage per gallon tanked with the lower octane fuels. i mainly use my truck to commute from Louisiana to Missouri (800 ish miles), with each passing tank, the distance to empty would drop during each fill up with lower octane fuels. on the return drives...it would climb back up as each fill up was restored with a higher octane. my truck has 36K as we speak....90% of those are these trips. otherwise, she sits in storage.
