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Old 04-05-2013, 07:01 PM
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Is it true that ethanol gives you less mpg

If it is true can someone explain why and what is going on in a scientific sense?

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Old 04-05-2013, 07:09 PM
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less BTUs in ethanol so takes more of it to generate the same power.same with propane
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Old 04-05-2013, 07:12 PM
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Ethanol has less energy per gallon than typical gasoline so unless you can use the ethanol benefits to improve combustion efficiency enough to overcome that energy loss you will get lower miles per gallon.

Ethanol does have high octane which can help improve efficiency if your engine has dynamic ignition timing controls to maximum efficiency including knock sensors that prevent to much advance. Most traditional engines, even those with EFI are not capable of this so they loose miles per gallon.
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Old 04-05-2013, 07:35 PM
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Quote:
Originally Posted by WICruiser View Post
Ethanol has less energy per gallon than typical gasoline so unless you can use the ethanol benefits to improve combustion efficiency enough to overcome that energy loss you will get lower miles per gallon.

Ethanol does have high octane which can help improve efficiency if your engine has dynamic ignition timing controls to maximum efficiency including knock sensors that prevent to much advance. Most traditional engines, even those with EFI are not capable of this so they loose miles per gallon.
Thanks, that makes sense.
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Old 04-05-2013, 08:26 PM
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All I know is every November 1st when winter blend is sold, my mpg drops 13%
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Old 04-06-2013, 06:48 AM
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All I know is every November 1st when winter blend is sold, my mpg drops 13%
Really, that much? You checked your odometer too?
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Old 04-06-2013, 03:46 PM
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Originally Posted by rusthater89 View Post
Really, that much? You checked your odometer too?
Winter blend changes the hydro carbon mix of the gasoline to favor more volitile ingredients so the engine will be easier to fire up when it's cold. The ethanol has not much to do with this in a 10% blend, it's there to bring more oxygen into the reaction to get a more complete burn without having to lean out the mixture.

The loss of mileage is mostly do to the high volitile blend, longer warm up times, and higher rolling resistance of transmission and rear end oils, tires, and wheel bearings, not to mention that when the tires have to sipe water and or snow the rolling resistance goes way up. So the cost of all this is you use the fuel less efficiently in a cold engine and you use more power to overcome the net resistance from the crank pully to where the rubber meets the road.

Ethanol does not help the operating octane much, it has a high Reasearch number of 109 but it Motor number is only 89, the rating at the pump is RON+MON/2 which for 100% fuel grade ethanol is 98.5 octane. Mixed as at 5 to 10% percent of gasoline that rating contributes very little toward octane improvement. E85 with premium unleaded gets about 94-95 octane so there isn't anything magic going on because the ethanol is close to premium unleaded it has very small effects. Another characteristic of ethanol is that its octane drops rapidly as its temperature goes up. So it just doesn't contribute much to detonation resisitance, for that you need to move up to methanol.

Also given the effects of cam timing are so intertwined with compression ratio and combustion chamber design, to utilize high octane fuel at their fullest level takes a lot of careful design and attention to detail when building an engine, this isn't something you can just add on parts get all the results.

Bogie
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Old 04-06-2013, 05:23 PM
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A couple of years ago my wife and I took a trip from St. Louis to Oklahoma City (NSRA OKC Nats). Started out with a full tank - 10% ethanol just about everywhere here. I checked the mileage as we went. Filled up around Lebanon Mo, noticed no ethanol sticker on the pumps. We got around 27 mpg. We got to OKC, drove around town and attended the Nats. Filled up on our way out of town - again, no ethanol notice on the pumps - we got 29 mpg (despite the city driving). Drove back to STL, stopped for gas outside the metro area - no notice again - we got 33 mpg. After we were back home, and filled up over the next few days, I checked again, we got 34 (again with some city driving). As the mix in the tank contained less and less ethanol, our mileage went up. As we went through the next couple of tankfuls, I noticed our mileage had gone back down (around 25 with about half city driving). Funny, the stuff with 10% ethanol wasn't any cheaper, but with the reduction in mileage actually cost more.
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Old 04-06-2013, 05:48 PM
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I might buy your colder weather has the most to do with reduced gas mileage, but I have also noted that the last two Novembers here have started off way above normal temperature wise. MPG dropped on November the 1st even though temps were on the warmer side. I am no scientist, but much higher production prices to produce ethanol blend + much lower MPG = we are getting screwed twice imho!
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Old 04-07-2013, 07:20 AM
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Regardless of whether a gas has ethanol or not. You will always use more fuel in a cold engine.(choke on for carb or open loop for EFI) Also my experience, carb engine gets flooded on a 25F degree day and barely starts.(big waste of gas) Thanks everyone for the insight though. It was something I never really thought much about until a buddy of mine complained he was getting bad gas mileage and blamed ethanol. Of course I wanted to verify this.
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Old 04-07-2013, 07:21 AM
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Quote:
Originally Posted by sedanbob View Post
A couple of years ago my wife and I took a trip from St. Louis to Oklahoma City (NSRA OKC Nats). Started out with a full tank - 10% ethanol just about everywhere here. I checked the mileage as we went. Filled up around Lebanon Mo, noticed no ethanol sticker on the pumps. We got around 27 mpg. We got to OKC, drove around town and attended the Nats. Filled up on our way out of town - again, no ethanol notice on the pumps - we got 29 mpg (despite the city driving). Drove back to STL, stopped for gas outside the metro area - no notice again - we got 33 mpg. After we were back home, and filled up over the next few days, I checked again, we got 34 (again with some city driving). As the mix in the tank contained less and less ethanol, our mileage went up. As we went through the next couple of tankfuls, I noticed our mileage had gone back down (around 25 with about half city driving). Funny, the stuff with 10% ethanol wasn't any cheaper, but with the reduction in mileage actually cost more.
What car did you drive?
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Old 04-07-2013, 11:12 AM
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The car on that trip was a 2009 Toyota Matrix 2.4L 4 cylinder with a 4 speed auto. We were just spectators that year.
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Old 04-07-2013, 11:15 AM
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The car on that trip was a 2009 Toyota Matrix 2.4L 4 cylinder with a 4 speed auto. We were just spectators that year.
Oh ok, just curious.
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