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My choice would be the 91 octane 100% gas. It's not all about octane and either one has enough octane for street worthy compression ratios anyway. I have noticed 2 - 3 MPG improvement when using 100% gas. The whole ethanol thing just rubs me the wrong way. Be glad that you have a choice.
Captsluggo
If I'm not mistaken the jury is still out on the damage to seals and o rings with ethanol over the long term. I go with 100% gasoline when I can get it.
I work for a division of General Motors and I'm pretty sure virtually every car manufacturer adapted to ethanol a number of years back. It still causes some issues with seals, etc. in the earlier vehicles... talk of more than 10% certainly won't do anything good to most present engines. I would like to think HD adapted to the current standards a few years back. Now with that being said, I personally have NO use for anything in my gas BUT gas. Unfortunately, I know of no service facilities selling "straight" gas other than just regular grade. If non-ethanol were available around here in high octane, that would be my choice!
As long as the Ethanol (grain alcohol) content isn't more than 10% - you're fine...even states in HD owner's manual. From your choices - I'd go w/93 octane...
Straight gas for my bike...if possible.
I like Shell gas and I can get 93 Octane without ethanol close to home, at least that's what the label says (doesn't say "contains 10% Ethanol")
There are no service stations with ethanol in my area that I'm aware of. I have found that 93 octane yields the best fuel mileage but the cost increase doesn't justify the difference. I've used Shell and found that my scoot does run as well with the nitrogen enriched fuel. My Harley has been getting terrible fuel mileage in this extremely hot weather we've been having. I’ve talked to guys that say Shell is the best fuel they have ever used. Go figure!
Now that NASCAR is using Ethanol blend this year, the Crew Chiefs have to schedule more frequent pit stops than previously. Milage dropped from 4.5 mpg to 4 mpg, (if what they showed a couple of weeks ago is accurate.)
We shouldn't be any different. Ethanol decreases milage apparently.
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