Thoughts on E15 Fuel

[ChrisB351]

Ethanol may be cheaper but your mpg wont be as much so itll balance out

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[ColeTrain84]

I've put E15 a few times. Here we have 88 octane with 15% ethanol and i noticed no difference in mileage or power. We have 87, 88(E15) and 91. Some places have 92 or 93 but those are more rare. I still average 18 mpg with whatever goes in it.

 

[bytheway]

85 octane gasoline is different from E85. I guess because both contain the number 85 folks can get confused

E85 is 85% ethanol and 15% gasoline. Only "Flex fuel" vehicles should run ethanol blended fuels higher than E15 (15% ethanol and 85% gasoline).

The reason you can run 85 octane gasoline (regardless of the ethanol percentage) at high altitude is because the air is thinner and consequently the compressed pressure inside the combustion chamber is lower. The lower compression pressure reduces the chance of pre ignition (knock) which is what a higher octane fuel helps prevent.

Running Colorado 85 octane gasoline is perfectly fine. When you drive to lower altitudes then purchase the 87 that is offered.

Disagree, a forced induction engine makes up for the loss of air density. I would not run 85 octane fuel in a turbo engine.

 

[P52Ranch]

If

Disagree, a forced induction engine makes up for the loss of air density. I would not run 85 octane fuel in a turbo engine.

If you were still getting full combustion chamber pressure at altitude I would agree. However, the incoming air pressure for a turbo is lower at altitude just like with a NA engine. In Denver the intake has approximately 3 psi less air to compress compared to sea level. This same three psi delta carries through the intake manifold after the turbo boost is added.
(The wastegate still opens at the same boost pressure delta as at sea level.)
Consequently there still will be a lower combustion chamber pressure at altitude with a turbo. This is evidenced by the turbo's drop off of engine HP at altitude. That drop off is much less noticeable than the drop off of a NA engine at the same altitude.

If you are pushing your engine hard all the time and looking for maximum horsepower then use the premium fuel regardless of altitude. Ford publishes different HP numbers for premium vs. regular octane on these engines. The knock sensors will reduce the engine performance to keep the engine operating in parameters.

 

[Silver-Bolt]

Here in Portland, we used to have "winter fuel" which was E15. Whenever the E15 hit the gas station our fuel economy dropped 15-20%. Now they mandate the E15 year round.

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