To E85 or not to E85? - Page 2 - Mercedes-Benz Forum

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post #11 of 13 (permalink) Old 11-08-2010, 11:08 PM
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Originally Posted by MGD View Post
I know this is an old thread but you guys need to give your head a shake here. The only advantage of E85 is easier on the environment. You do not get better fuel economy and you definitely do not get more power than premium.

Do a little research and you will see that ounce per ounce 91 has more potential BTU (actually WAY more) than E85. E85 has an octane rating of 87, where as 91 guessed it...91. This means less detonation, which means less retardation, more power. That's not taking into account the BTU thing....

My .02c

You are incorrect. First, pure 100% ethanol is 105 to 113 Octane. Nascar even claims 113 Octane using E100 at the track. The variance is all due to moisture content. Alcohol is hygroscopic; it soaks up moisture. If you have a FFV you can actually go to a liquor store and buy pure spirits that is 92 Proof and put it in your tank. They mark it as 92 Proof when it is actually 100 Proof in the sealed bottle. However, they have to mark it as 92 because once you open it the alcohol begins to take on moisture. Within days it will take on enough moisture to settle in at 92 Proof. It's a good idea to buy some of this, place it in a yellow gas can (1 or 2 gallon size) and keep it in your trunk for emergencies. You should not do this with E85 since up to 30% of it will be gasoline.
Your E85 is blended 87 Octane gas and E100 which is pure Ethanol. Her is the breakdown:

E100 at 85% (113 octane pure ethanol)
Regular at 15% (87 octane)
Final Summer Blend: 109.1 octane

E100 at 70% (113 octane pure ethanol)
Regular at 30% (87 octane)
Final Winter Blend: 105.2 octane

Other benefits besides the environment are:
- Cooler running engine
- Less carbon build-up; much less. In fact the ethanol will keep every part of the combustion chamber spotless. No need for STP gas treatment.
- Less expensive as to run as long as your above your break-even. For example, my 2001 CLK320, running a FuelFlex converter box, loses about 10-15% in mileage per gallon of E85; 15% local streets and 10% highway. I pay $2.70 now for E85 and 93 Octane is $3.35. The difference is $.25 per gallon based on the loss in fuel consumption. That's $.25 saved per gallon. When I was paying $2.15 this summer and 93 Octane was $2.99 per gallon I saved $.52 per gallon. That's a net savings of $9.36 per tank. Again, the savings are longer engine life, more HP at the wheels and yes, a cleaner car!
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post #12 of 13 (permalink) Old 11-09-2010, 03:31 AM
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Yes, E100 is a more powerful fuel compared to 91 octane because of it's properties, but you can't go to the pumps and get E100, you can only get E85 (well you can't get either in Canada, :P ) and that's where this fuel loses it's advantage.

Why Fuel Mileage Drops with E85 - Fuel Economy is Less with E85 - Fuel Economy is Lower with Flex-fuel Vehicles
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post #13 of 13 (permalink) Old 11-09-2010, 03:03 PM
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Since I posted so early this morning, I will elaborate.

I must admit, I do not have first hand experience with this subject. All I have is from what I read. What I read is E100 can develop a lot of power due to it's higher octane rating and cooler running (also meaning it is going to run in a much higher compression engine than most of us use as daily drives). Makes sense, but when we compare E85 and 91 this is where we run into problems from what I have researched.

Since most higher performance (albeit daily drive) engines are optimized for 91/93 fuels the E100 is cut with gasoline to make E85 at which point detracts from the true potential available in alcohol fuels. When you factor in the lower available energy (in BTU) from E85 as opposed to 91/93 (and the fact that "normal" engines run at lower compression than their alcohol based counterparts) you still end up worse off power wise than 91/93.

I think I understand it, correct me if I'm wrong. Alas you have the upper hand somewhat due to first hand experience. Any input is welcome as there is a lot of misconceptions around this issue, and the more info people receive the better there choices. Including mine

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