Quote:
Originally Posted by 69ZLover
So one tank of regular 92 down. Noticed no performance issues. What I did find odd was this, I now average 13.1 MPG where before for the first 5k of millage all on clear premium I was always in the 17.1-17.8. One more tank is in order to kinda proof this out on my car. I never left town on this tank so a road trip of some sort is in order.
Did some math as well and the cost savings of going regular premium will pay for 1 can of Torco which will get you a tank of 96 octane for you penny pincher's who want cheap performance.
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Quote:
Originally Posted by jessrayo
Okay, the real difference is in the energy of the fuel. Alcohol has less potential energy per gallon than gasoline. E85 has about 80% of the potential energy per gallon as gasoline. To put it simply the explosive power of gasoline is greater than any alcohol. There are several different types of alcohol and ethanol and methanol are a couple of the more common motor fuels. The big advantages of alcohol (other than the fact it can be distilled from plants rather than pumped from oil wells) are that alcohol can handle more compression without knocking (gives it a better octane rating) and it burns efficiently with less oxygen than gasoline.
When you think about what we do to cars to get more power, the vast majority of upgrades are designed to get more air into the engine. Intakes, cams, superchargers, etc. When the fuel burns efficiently with less air then you can pump more fuel in the engine to match the air you have and it works fine, frequently giving you more total power because you are spraying more fuel into the same air. This is what happens when you convert to E85. You put in bigger injectors and fuel pumps and change the air fuel ratios in the tune so the car gets much more fuel per unit of air.
Alcohol gets less mpg because you have to inject more for air/fuel ratios and it has less potential energy per gallon.
This is the short version.... I keep thinking of things I could say about residual compounds of incomplete combustion and other things but the bottom line for me is the car will get a little better mpg and have a little more power with pure gas if you can find it.
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jessrayo is correct that you need more fuel for the same power with Ethanol, but at 10% with 80% potency of gas, your gas mileage should only be impacted by 2%, not 50%.