Originally Posted by Grubrunner
Maybe I can help... Higher octane gas actually has slower more controlled burn characteristics and is designed for engines with higher compression and or more advanced timing. Running 91 octane gas when the engine was designed around a faster burning (89 octane) fuel, will technically slow it down, unless its tuned (advanced timing, etc) for that octane rating. Although I'm not an expert, so I may not be 100% correct on this.
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