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I am just curious, Does the 10% alcohol in gasoline change the miles per gallon meter. My father has a chevy impala and it was just recalled for that very reason. they need to change a chip in the computer so the calibration is correct! I am currently looking for a used insight.
David
 

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High David . Good luck in your search. :D

Alcohol in the gas does decrease mileage but only one or two percent. There is simply less energy in the alcohol by volume so changing a chip probably won’t help, though it might help some cars run smoother. The British rally team that won the 1,000cc class with an Insight were running 85% alcohol!!!

See:

http://www.motorsportdevelopment.co.uk/ ... g/2/id/222
 

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the meters "read" the fuel going into the engine and divide it into the miles you drove. Hence if you're getting fewer miles/gallon, that's what will show up on the MPG gauge.

The EPA's own website (see below) confirms that reformulated gas gives a mileage hit.

"RFG contains oxygenates, which contain less energy per unit volume than conventional gasoline. The table below outlines the differences in energy content between RFG and conventional gasoline based on the three most widely used oxygenates. ..."

They claim (using optimism...) that a five percent ethanol blend causes a 1.9 percent drop, suggesting that the current ten percent ones would give you a four percent one. I've done long distance highway trips gassing up with (where available) "real" gasoline and the RFG, and have noted significant differneces while traveling.

(NOTE that you can't be sure what is actually getting pumped. The stations mix and match and one that's giving you "real" stuff today may get a cheaper load of RFG tomorrow, and vice versa [except in areas where all gas has to be RFG])

EPA info:
Linkname: EPA - OTAQ - Fuel Economy Impact Analysis of RFG
URL: http://www.epa.gov/otaq/rfgecon.htm
 

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The octane rating of the gas is the same, so no change is necessary for the tuning with the ~10% ethanol fuel in pumps today

if you ran E85 then you would need some higher compression pistons to take advantage of its higher octane, not just a retune.


james said:
It shouldn't change the meter readings at all, though, should it? I thought that was computed from counting the volume/duration of the injectors, so a gallon of anything going through them should give the same readings, no?

I would think the chip changes would be in order to have proper engine timing &c for fuels with ethanol.
 
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