Switching between E85 and gasoline

[Z-Michigan]

accidental double post, please see below post

 

[Z-Michigan]

From GM service document # 2000114 (these a excerpts)

For 2006, GM has changed the method of "sensing" the alcohol content of fuel in E85 compatible vehicles.

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Switching Between Gasoline and E85
No special precautions need to be taken when switching back and forth between gasoline and E85 other than re-fueling events must be 11 Liters (3 gallons) or greater, and the vehicle must remain in closed loop long enough (usually by the time the vehicle has been driven for 11 km (7 mi) at full operating temperature) to comprehend and calculate the composition of the new blend in the tank.

For best driveability, the vehicle should be driven for at least 11 km (7 mi) following a refueling event when switching between gasoline and E85.


----SNIP----

KAB - extremely useful info, THANK YOU!

Based on where I live and get fuel, 99% of the time I will be driving >7 miles after a refueling, so it sounds like I have no real concerns beyond that.

I didn't want to bias answers by saying why I am so interested. In my two test-tanks of E85 so far (each about 13 gal in my 31 gal tank, so actual ethanol % in tank was around 30-33%) I saw less of a decrease in mpg vs. what would be predicted based on the substantially lower energy content of ethanol. I am keeping very detailed records and calculating things with a spreadsheet, keeping track of % ethanol in the overall fuel tank (assuming homogenous blending from tank shaking with vehicle while driving) and also calculating energy content of the resulting fuel based on standard info that ethanol has only about 65% energy content of gasoline.

One complication here is that I assume most gasoline is now between 5 and 10% ethanol based on phase-out of MTBE as an additive, but no stations label at less than 10% and I'm not sure if all do at 10% ethanol. I am assuming that my gasoline is 5% ethanol if not marked as a higher %. If there still exists gasoline that has no ethanol content, I would be interested to know.

Anyway, the local price of E85 is too high (only 30 cents less than regular) to be worth purchasing if you get only 2/3 the mileage on E85 as you would get on gasoline. However, since my mpg is dropping less than would be predicted by the energy content difference, I am still measuring whether I might break even on E85, or at least come close enough to not worry about the cost per mile difference. In case anyone is scratching their head at why mpg might not drop in direct proportion to energy content, my best guess is (1) octane is dramatically higher with significant ethanol % and therefore ignition timing advance may be significant based on knock sensor, thereby giving better thermal efficiency; and (2) if #1 is correct, because my engine also has the "AFM" V4 system, running higher octane may allow more time in V4 mode and therefore also help mpg that way. These are just guesses.

 

[Boiler74]

One thing you might want to consider in doing your calculations is the "winter blend" of E85. It's actually E70. That difference will give you a little more economy in the winter over the summer. Like you I played with my 04 Suburban and E85, hoping to find some savings. Just wasn't there, at least not in the summer. I don't know about with the winter blend.

Here's a link for you.

In This Issue

It has a section about winter blend.

 

[Z-Michigan]

Thanks, Boiler. I was aware of the winter E70, though I don't know exactly when its use starts and ends. Useful link - I'm reading all I can on this.

This may sound a bit cynical but I'm not looking at E85 because I think it's going to be cheaper based on production or all that much better for the environment - instead, I think that in my area and the rest of the midwest there are far too many ethanol plants being built and too much corn being planted, and I'm hoping that for 1-3 years there will be an ethanol glut and lower prices due to supply. Long term I am hopeful that cellulosic ethanol will actually make both economic and environmental sense, but for now I don't see corn ethanol making either.

 

[number two]

Z-Michiganerhaps I can share a little information. I deliver tanker loads of petroleum products in Northern Michigan.
I was surprised to learn that not all gasolines contain MTBE,even though it will be banned after this year. I thought that ethanol would be required to oxygenate the fuel but apparently not necessarily. We often load in Cheboygan and Traverse City,MI. Both terminals are filled by a boat from the huge BP refinery in Whiting,IN. I was recently asking the T.C. terminal manager if they'd have ethanol by Jan '08 and he said sometime in '08,but BP's gasolines they receive haven't had MTBE for awhile. Surprised me-I was thinking ethanol was the replacement for MTBE as well as an attempt to reduce oil usage.
Straight gasoline is still sold up this way at many stations. If the trucks load up here,there is no ethanol at the terminals so gas is what you load. Many trucks go downstate to load the 10% ethanol gas and haul it up here. Usually the wholesale price in say Bay City or North Muskegon is just enough cheaper to make it about break-even whether to load locally or load 150-200 miles away. all depends how much you want to run your trucks.
But you can get the ethanol blend there and I believe there is(or was)a 6 cent road tax break on the ethanol blend. That's big money in this business. Probably 30% of the stations up north have ethanol already. I just went down for my first load of ethanol this week. We're switching about half our stations over that are further south. Upper Peninsula will still have gas for now. Interestingly enough,they mix 84 octane gas with 10% ethanol to get 87 octane regular.
I hope this wasn't too boring and maybe answered some of your questions. Good Day

 

[Z-Michigan]

#2, that is extremely useful info and not boring at all. And especially interesting since you're in Michigan. I guess I will assume that my gasoline is 0% ethanol unless it's marked on the pump (mostly Sunoco stations, which have indicated 10% ethanol for a while, at least on regular 87 octane).

This actually makes my E70/E85 gas mileage experience look even better, because I had been calculating the difference compared to regular gasoline by assuming that unmarked gasoline was 5% ethanol, which of course slightly lowers its energy content. At some point I will try to post my spreadsheet to show the calculations and unexpectedly small difference between mpg on gasoline and mpg with 1/3-1/2 E85 (or E70) in the tank.

 

[number two]

Z-Michigan: Glad you found that useful info. I forgot to mention that I don't believe the stations are required to label ethanol content at the 10% level. We just started ehtanol blends this week and I saw no labels. We can haul up to 20% ethanol blends with the same number in the red hazmat placard on the trailer. Ethanol blends are available at Bay City,Lansing,Jackson,North Muskegon,and others. My guess is if you're near any of the terminals that have ethanol,odds are the gas you're getting is an ethanol blend. Ask station manager or transport driver to be sure.

 

[Z-Michigan]

I live between Lansing and Jackson and I'll bet 99% of the gas I buy comes from one of those terminals. Interesting. Time to start asking the station attendants - hope they know!

 

[excelagator]

This may sound a bit cynical but I'm not looking at E85 because I think it's going to be cheaper based on production or all that much better for the environment - instead, I think that in my area and the rest of the midwest there are far too many ethanol plants being built and too much corn being planted, and I'm hoping that for 1-3 years there will be an ethanol glut and lower prices due to supply. Long term I am hopeful that cellulosic ethanol will actually make both economic and environmental sense, but for now I don't see corn ethanol making either.

I agree with you on corn not being the cat's meow for ethanol. Food prices are up because of ethanol from corn. Think of anything with corn in it or raised on corn. Examples, Eggs, pancakes, and yes kethup!!!

1 gallon of ethanol from corn uses 2 gallons of fuel to produce
16 gallons of ethanol from sugar takes 1 gallon of fuel to produce
22 gallons of ethanol from switchgrass takes 1 gallon to produce

Switchgrass can be grow in 75% of the US, so plant switchgrass guys!!

We recently bought a 08 Silverado with the flex-fuel option for my wife. I think ethanol from corn is decent step in the right direction. I am supporting local companies building the plants and most of my money is staying here.

Maybe Omar can pay $100 for a bushel of corn!!! LOL

Dan