Gas-alcohol effecting mileage - BMW Luxury Touring Community
 
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post #1 of 7 Old Apr 19th, 2008, 7:52 am Thread Starter
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Gas-alcohol effecting mileage

I'm wondering if my mileage has gone down lately because of the fact that so many local stations are now substituting gas-alcohol for pure gas. Seems like I read that the burn of pure gas compared to gas-alcohol is about 85% of the efficiency? That might explain why my mileage seems to have slipped from about 45 to 41.

I haven't really made any detailed measurements and I'm only basing this on fly by the seat observations of my on-board computer. Seems I fill up a little more often. Maybe it could be the O2 Sensor?

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post #2 of 7 Old Apr 19th, 2008, 8:43 am
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Re: Gas-alcohol effecting mileage

Yup, that could be it. Ethanol through corn is a lose, lose situation. I could probably tack another lose on there for all the beef and swine farmers out there that are going bankrupt as I type.

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post #3 of 7 Old Apr 19th, 2008, 9:06 am
 
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Re: Gas-alcohol effecting mileage

I noticed that when I switched to Shell at Santa Fe NM, on the way back to Nebraska from Escondido, CA, my mileage went from around 45 to 50.1 in three tank fills. There were no signs on the premium pumps about using ethanol at the Shell stations like there were at other brands. Maybe the higher elevation may have been a factor also.
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post #4 of 7 Old Apr 19th, 2008, 9:10 am
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Re: Gas-alcohol effecting mileage

I also get the best mileage from Shell.
Chevron is second best.
Although in the winter months, in some states, Shell adds ethanol and the mileage goes down. (some stations have a sign indicating what months)

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post #5 of 7 Old Apr 19th, 2008, 10:37 am
 
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Re: Gas-alcohol effecting mileage

Quote:
Originally Posted by dandiver
I'm wondering if my mileage has gone down lately because of the fact that so many local stations are now substituting gas-alcohol for pure gas. Seems like I read that the burn of pure gas compared to gas-alcohol is about 85% of the efficiency? That might explain why my mileage seems to have slipped from about 45 to 41.

I haven't really made any detailed measurements and I'm only basing this on fly by the seat observations of my on-board computer. Seems I fill up a little more often. Maybe it could be the O2 Sensor?

Definitely. Pure gasoline has about 125000 BTU/gallon where ethanol is around 75000. So at 10% ethanol (125000X.9) + (75000X.1) = 120000/125000 = .96

You're losing a bit more mileage than the math suggests, but the above is a big chunk of the difference. Remember, government coffers are filled by the taxes per gallon. So the last thing they want is for us to start buying less fuel. Gotta make up the difference in extra mileage being attained on cars somehow. The ethanol energy policy makes absolutuletly no thermodynamic sense. It takes more combined energy to produce than it contains.

Corn and grain were put on this spinning rock to eat (fuel for organisms), not for mechanized transport fuel. Now the costs for food are soaring, but that was the whole idea you know. Well, at least our government isn't as stupid as others (China's cultural revolution) where millions starved due to official policy blunders. But I still often wonder how far the boys in DC are willing to push their luck with their corporate/Wall St. payoffs. At $6 gas and $10 milk , I think some folk will be planning to get all "Mussolini" on their buttocks.
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post #6 of 7 Old Apr 19th, 2008, 8:41 pm
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Re: Gas-alcohol effecting mileage

Quote:
Originally Posted by Sofitel505
So the last thing they want is for us to start buying less fuel. ... It takes more combined energy to produce than it contains.
Conspiracy! Conspiracy!

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post #7 of 7 Old Apr 19th, 2008, 9:44 pm
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Re: Gas-alcohol effecting mileage

Quote:
Originally Posted by dandiver
I'm wondering if my mileage has gone down lately because of the fact that so many local stations are now substituting gas-alcohol for pure gas. Seems like I read that the burn of pure gas compared to gas-alcohol is about 85% of the efficiency? That might explain why my mileage seems to have slipped from about 45 to 41.

I haven't really made any detailed measurements and I'm only basing this on fly by the seat observations of my on-board computer. Seems I fill up a little more often. Maybe it could be the O2 Sensor?
I see a real difference when I get the 10% stuff in Delaware vs the gas in MD. About 4 mpg less on the gasohol. Farmers have a real challenge trying to feed the world, let alone our tanks.
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