Flex fuel in non flex fuel engine?

I recently put a few gallons of flex fuel in my 1998 Honda CRV by accident. What, if any, effect will that cause? I recently noticed a reduction in MPG also. Could that be related?

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Just a few gallons probably won’t hurt anything. The reduction in fuel mileage is normal becuase E85 has less energy per gallon than gasoline or E10

The MPG reduction continues even after a few tanks of regular fuel.

Did you fill it up the rest of the way with normal gas (or at worst E10) right away? If not, do that now.

It may be a long shot, but you may want to replace the fuel filter. I doubt if you caused any damage.

I forgot to ask. When you put in that few gallons, was that added to a nearly full tank or a nearly empty tank?

You will find a lot of gas pumps these days have a sticker that reads, “Fuel may contain up to 10% ethanol.” As long as you keep the amount of ethanol below 10%, you should be fine. How much has your fuel economy declined? How many tanks of fuel have you measured?

You really can’t accurately measure fuel economy over one or two tanks of fuel. You really should calculate it over many tanks of fuel, and even then it is only an estimate. You can’t possibly measure distance and fuel accurately enough to get a precise calculation.

My wife once refueled our Subaru, which is not a flex-fuel vehicle, with E-85. (She found the only E-85 pump in 500 miles.) The resulting mix was probably two thirds ethanol. The car ran OK and, as soon as I found out about it, I refueled with 87 octane regular. The experience hasn’t hurt the car. A steady diet of E-85 would cause problems.

wouldn’t it be better to richen up the mixture with a higher octane, since the e85 has less?

I don’t think that is the issue. I think the issue is that with high concentrations of ethanol, rubber parts will corrode. But yes, using high octane gas would be a good idea anyway.

E-85 averages about 100 octane.

High octane is not a fix all. High octane is not BETTER than low octane. High octane does not have more power than regular.

High octane means only one thing. The combustion will take place a little slower to prevent knocking when the timing is set early to gain a little more power from the engine.