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My black Max is EFI and it is already converted to pre mix. I have ran 89 octain could I or should I run 93 ?
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If you're burning E-10, what you have to consider is that if you ever get enough water in the tank to combine with all the ethanol, so you'll lose up to 4 points of octane!
That means your "89" octane fuel is really only 85 octane, so you'd be at risk for detonation (which you can't hear on a 2-stroke, since there are no valves to rattle), since that motor is probably designed for a minimum octane of 87! Detonation is the "pinging" you hear in your car if fuel is too low in octane, and is bad news for the motor, as it puts very high shock loads on the rings, pistons and bearings! However you'd be ok with losing 4 points from 93 octane fuel, ASSUMING it really has the advertised "LESS than 10% moonshine" in it!
This last assumption can be significant. I believe the ethanol is added at the distributor, so you're depending on a human that's not hung over or high on it, to add the right amount of gallons of moonshine to the tanker truck! After reading Fr. Frank's post on
ethanol-related problems on his motor, I got one of these
ethanol testers and check the ethanol content of the gas every time I refuel. Fr. Frank's mechanic said that even if you use a fuel preservative like Stabil or Startron, THEY DON'T WORK if ethanol level is over about 7%! I've never found more than about 6% at the stations I normally use, but given the cost of potential repairs, I figure the cost of the tester is a good investment!
One other tip . . . water in the fuel is also bad news for fuel injectors, so make sure you have a good filter like a Racor with the plastic bowl with drain so you can check to see if you're getting water in the fuel! BRP has added a water separating filter and water sensor on the newer E-TEC's and I'm thinking about adding one of those kits to mine. I believe other engine makers have done the same to theirs also.
Buying non-ethanol gas from a marina is no guarantee it won't have water in it! On my 700 mile circumnavigation trip last year, I burned non-ethanol gas the whole trip, but I checked the filter every time I refueled. I found water after refueling at Clewiston, St. James City, Gasparilla Marina, Sanibel, and Chokoloskee! From Flamingo on and back up the east coast, I found no more water.