by Jim Kreuz | photography by Tom Shaw
illustration by Christine Wilson
L
ike it or not, your favorite filling station
probably sells gas containing up to 10 percent
ethanol (E-10). What does ethanol do inside
your engine? Does it hinder the performance of your
fuel-injected engine? Is it harmful to your injectors?
What do you need to pay particular attention to,
whether you’re driving a new Mustang GT or a
vintage high-performance car, when running on
ethanol laden gasoline?
FUEL-INJECTED ENGINE
PERFORMANCE
Let’s spoil the ending of this article and give you the answers up
front. Basically, your fuel-injected engine can’t tell the difference
between 100 percent gasoline and E-10. And, it’s not harmful to your
injectors. Read on and you’ll find out why.
E-85 (70-85 percent ethanol), an alternate or flex fuel, is another
matter. If you want to run this type of fuel on your non–flex fuel
engine, you’ll need a fuel sensor (conductivity probe that measures the
ethanol content of the fuel), larger injectors, and a new chip that will
accept the fuel sensor signal. Oh, and you might want to swap out your
fuel filter after you’ve run through two tanks of E-85. The 85-percent
ethanol mixture does a good job of removing any gunk left in your fuel
tank from years of storing gasoline, and that gunk will get deposited
on your fuel filter.
The fuel sensor that comes with a flex fuel engine works in
conjunction with the oxygen sensor mounted on your exhaust.
Together they provide input to the chip that controls the fuel-to-air
mixture being fed to the engine. If you want to convert to E-85 on the
cheap, you can skip the fuel sensor addition ($300-$600) and have the
engine chip rely solely on the oxygen sensor for adjustment. You would
then “tune” the chip settings for a given fuel (E-85, for example).
DECREASED BTU VALUE
The heating value of a gallon of gasoline containing no ethanol
averages 114,000 BTU (a BTU, or British thermal unit, is the am