E85 Mix Calculator

E85 from a pump is rarely 85 percent ethanol. The standard allows anywhere from 51 to 83 percent and stations move to the low end in winter so engines start cold, so the pump percentage is an input here rather than a fixed number. Enter the ethanol content of both pumps and the blend you want, and this gives the gallons of each, or takes a tank that already has fuel in it and says how much to add. It also reports the finished blend, the energy per gallon against E10 and the stoichiometric air fuel ratio, with the reference figures printed beside them.

Calculator Type
Measured In

You are filling from empty and want a set ethanol content. This splits the fill between the two pumps.

Regular pump gasoline is E10 in most of the United States, and E0 where ethanol free fuel is sold.
Pump E85 runs anywhere from 51 to 83 percent ethanol and drops in winter, so use the figure from a content tester or your flex fuel sensor rather than 85.
E30 is the usual target for a stock turbo car on a flex tune; a flex fuel vehicle will take anything up to the pump figure.
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Measured In

There is already fuel in the tank. This gives the gallons to add to land on the ethanol content you want.

What the last fill was. If it was pump gasoline it is usually 10 percent.
Pump E85 runs anywhere from 51 to 83 percent ethanol and drops in winter, so use the figure from a content tester or your flex fuel sensor rather than 85.
Has to sit between what is in the tank and what you are adding.
In the same unit as the rest of the form. Leave at zero to skip the check that the fill actually fits.
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Measured In

You already poured. This says what is in the tank now.

Pump gasoline is usually 10 percent.
Pump E85 runs anywhere from 51 to 83 percent ethanol and drops in winter, so use the figure from a content tester or your flex fuel sensor rather than 85.
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