MPG loss with 10% ethanol--- 2

[blacksmith37]

Theoretically there should be a 3% loss of MPG when going from gasoline to 10% ethanol. I have recorded every tankful MPG for 115,000 miles. A few yrs ago our rural was required to add 10% ethanol (to buy corn belt votes), so I have 70,000 of MPG with real gasoline and 65,000 miles with 10% ethanol. ( Same driver, same driving pattern, modern state -of -art fuel inj 5.6L Nissan V8). By inspection (have not mathmatically averaged data) it looks like a change from 16.8 MPG to 15.2 MPG, or about >10% loss due to ethanol.
Is there a reason why 10%ethanol would reduce MPG by more than 3% ?

 

[dicer]

My hint was, simply, if the thing burns more fuel, someone makes more cash, that is number one reason for the alky being added.
I liked the excel comment above.

 

[patprimmer]

Wouldn't that be related to the relative amount of fuel burned times the relative cost of that fuel. I mean it's primary school maths. No need to be an engineer or even a technician to figure it out. Basic 10 year old child literacy levels are enough.

Regards
Pat
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[drwebb]

For those interested here is a handy reference map of US gasoline requirements:

http://www.mobil.com/USA-English/GFM/Files/US_Gasoline_Map.pdf

 

[dgallup]

Interesting, that's changed a lot since the last time I saw it.

Any idea what "No 1 psi EtOH Allowance" means?

Everywhere I've been that is in the white "Conventional" areas has up to 10% ethanol blends at 99% of the pumps.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[JSteve2]

Ethanol is more volatile than standard gasoline, and in many areas is allowed to test at a higher vapor pressure. I think those must be places where the allowance is not in place. If you can get your gasoline with ethanol to test within the standard, it can be used in those places.

This map is more about relative strengths of lobbying groups than anything fundamental about gas formulations.

 

[swall]

Ethanol has a Reid Vapor Pressure of 3, pure gasoline ranges from 5-15 and E10 is around 18. The increase that occurs when ethanol is added to gasoline is attributed to ethanol being polar.

 

[Duwe6]

I actually have not seen any mpg loss running E10. It will be acting like the old-time water-vapor injection that gave a small, but significant mpg increase. Ethanol is VERY hygroscopic, so it will always be 'wet'. The small ammount of water in the E10 blend will flash to steam and give you that 1,600x expansion and cool the exhaust gasflow. Puts more energy into the motion of the pistons, and less energy being blown off as hot exhaust gas. Internal combustion engines are heat driven. Every bit of heat you can keep at the pistons increases mpg.

E85 is a whole 'nother case. I see at least a 10% drom in mpg, and evaluate the price accordingly. Thus, E85 is seldom a bargain.

 

[patprimmer]

E10 theoretically gives about a 3% drop in fuel economy. Various aspects of tune and EMS can impact on that in a positive or negative way. Most people cannot really measure to 3% accuracy.

E85 if it is actually 85% ethanol theoretically uses about 30% more fuel. It is inconceivable that tune and EMS and measurement by any competent person could reduce that to 10% unless something was really wrong with the tune for the 100% straight hydrocarbon, alcohol free fuel

Regards
Pat
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[Lou Scannon]

Pat, I agree 100%.

 

[pontiacjack]

Where should I go to learn the terminology seen on that map?

 

[fermjohnp]

patprimmer,

Does it then even make sense to put E85 in ones tank if we are on aveage losing 30% efficiency?

 

[berkshire]

fermjohnp
Only if you can get it 35% cheaper.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[patprimmer]

Gee whizz berkshire, who would have thought on a site dedicated to working engineers with engineering work related problems to discuss, that anyone here could have done that mathematics so quickly. ;-)

Regards
Pat
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[Lou Scannon]

fermjohnp
Only if you can get it 35% cheaper.

... or are willing to pay a premium and have the skill & tools to take advantage of the higher performance potential! (-: