Posts: 3518
Location: north central wisconsin | VMS - 5/1/2014 11:53 AM
There is a ton of misinformation out there...
Minimum octane ratings are given to prevent an engine from detonating with lower octane fuel, such as 86 or 85 octane. I have seen lower octanes in other states (out west comes to mind) which is what you would want to avoid.
The higher octanes will not boost performance unless they are non oxygenated (non ethanol) but the increase in performance would most likely go unnoticed. Even then, if you found 87 octane that was non oxygenated, you would not notice any difference either.
Notable performance increase would take much more than just changing fuel. Engine parts would need to be changed or modified...much like Hydrotech marine does for Yamaha engines by offering shaved heads, exhaust tuners, carbon reeds, etc., and then at that, those parts due to the EPA are only allowed for testing or racing purposes only... I did that with a 90hp yamaha 2 stroke as I was looking to get every bit of performance out of that motor being the smallest displacement 2 stroke 90hp on the market.
Steve
Is there any way to safely modify a Yamaha 90HP 4 stroke to get more performance? I have one on a 690T Ranger and while it is fine, a tad bit performance would be invited. I regret not putting a 115 on it, but went with the legal rating. Doubt I'd do anything, as I love the way it runs and don't want to lose any life expectancy, but just curious.
I run 89 Octane non oxygenated fuel and seem to see my best performance for price with it. The highest octane non oxy's haven't shown me any better performance and in fact the 89 has bench tested better starting/running in my ice augers and lawn eqpmt.
Edited by Reef Hawg 5/1/2014 12:16 PM
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