E85 fuel economy observation

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Long story short, I had to get a new van. Gone is the 2009 Chrysler T&C 3.8, now have a 2016 Grand Caravan 3.6. On the trip home from Minneapolis area, I was averaging 24-25 MPG. Stopped an hour away from home. Topped off with E-85 since it is a flex fuel vehicle. Price difference was 46 cents per gallon. Just wanted to see what the MPG difference would be. MPG dropped to 15-17 MPG. Not saving any money at that rate. Will top back off with reg. fuel when the tank gets to the 1/2 mark. I had heard that E-85 had to be $1 or more per gallon cheaper to save money due to the poorer fuel economy. I also heard that E-30 seems to be the optimal blend. May try it sometime just out of curiousity.
 
Does anyone here have any long time experience with E85? Does it do anything useful besides burning up some corn or whatever? In the real world does it run cleaner? Does a vehicle suffer maintenance wise? Does E85 accomplish anything?
 
You can run more boost in turbo engines. A little bit more power in naturally aspirated engines. I'd run it in my cars if I could get it.
 
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The problem is that ethanol has a MUCH lower Energy Density, and thus is incapable of providing the power output of gasoline, in most situations.

In high compression environments, as well as cars that can dynamically adjust timing, there are advantages to using ethanol.. but for your average minivan, you won't really see it.



As you can see, Gasoline has an Energy Density of 34.2 Megajoules per Liter, whereas Ethanol is only 20.9 MJ/L - about 61%. E85 is 85% ethanol, so you'll see a bit more.. about 67% the power/MPG of pure gasoline.

This is also why typical gasoline, with ~10% ethanol only provides about 95% the MPG you get out of pure Gasoline.
 
Whether E85 is worth it or not is more of a regional thing. When the price spreads are there, it can be a plus to use E85. When we had our insanely high gas prices a few years back, I used E85 exclusively. With over $1 price spread and only a 3-4 mpg hit, it was more than worth it.

EPA claims that emissions are cleaner from ethanol fuels. I really don't pay much attention to that stuff. I don't live in a major metro area. And I did live thru the 60's / 70's, and air is a lot cleaner now than it was then, in just about every part of the country. Whether the mix of ethanol in gas contributed to the pollution decline, I have no clue.

I keep waiting for one of the OEM's to finally jump on a engine specifically designed for E85 and not just these either / or flex fuel engines. Cummins has had a 2.8L inline 4 E85 engine for awhile that has a power output equivalent to the 5.7L Hemi engine, and gets almost diesel equivalent fuel economy. Ricardo played around with a V6 E85 engine that could almost match a 6.6L Duramax in performance and fuel economy. They ran it in several 3500 GM pickups. When the engine is designed to take full advantage of E85, it can be a real eye opener. The BTU level of a fuel is a factor, but other characteristics of the fuel, when taken advantage of, can make the BTU equation moot. And even in the flex fuel engines, they seem to be somewhat dependent on the design and ECM parameters as to how much affect there is on fuel economy between E0 and E85. My 2015 2500 6.0L will average around 14 mpg for all miles on regular. It averages around 11 mpg on E85. Regular E0 gas is going for about $2.51 in my area now. That would be roughly a 18 cent a mile cost. E85 is going for about $1.75 in my area. That equates to a 16 cent a mile cost. Hadn't looked at it for a while. May need to go back to E85.

Putting E85 into a engine primarily designed around gasoline is a total waste unless the price spreads are good.
 
E85 has 100-105 octane (R+M/2), so an engine designed for it can have considerably higher compression.
I suspect an engine set up for E85 would need so much timing retard for 87-93 octane that it would cause other issues.
Perhaps a GDI engine with 13:1 or more compression would make the best of both fuels.
 
Higher compression (or just higher cylinder pressures) would lead to more NOx I'd think. Which a 3 way catalyst can handle, but I'm not sure what the trade-offs are (need to run less rich to make the chemical equations work out?).
 
Originally Posted By: circuitsmith
E85 has 100-105 octane (R+M/2), so an engine designed for it can have considerably higher compression.
I suspect an engine set up for E85 would need so much timing retard for 87-93 octane that it would cause other issues.
Perhaps a GDI engine with 13:1 or more compression would make the best of both fuels.


That is true. The E85 specific engines I have seen thus far are creeping into diesel arena for compression ratios and boosting on top of that. But also delivering diesel equivalent performance and fuel economy. I am not privy to how they do it all, but when an engine is designed for high ethanol concentrations, the typical stuff we think about ethanol and fuel economy goes out the door.
 
Wild guess: static compression is different than dynamic. Atkinson cycle engines run high static, but hold the intake valve open longer than usual, so that the intake charge is reduced (and presumably expansion is increased). With VVT the manufacturer can play with what goes into the cylinder and keep pressures below knock.
 
Originally Posted By: turtlevette
You can run more boost in turbo engines. A little bit more power in naturally aspirated engines. I'd run it in my cars if I could get it.


The Caprice is setup to run on either. I wish I could get it here.
 
I had my Tahoe ppv 5.3 flex fuel tuned to take advantage of the higher octane. The truck prior to the tune got 15.3 highway 87 octane. After the tune the truck got 15.5mpg on E-85. At the time E85 was about $1.25 gallon less just compared to 87 octane. 93 octane produced 19.6mpg. But with the higher cost of the premium gas the truck needed to get 23+mpg to net the same fuel cost per mile. I ran e85 for yrs and about 75k miles. No issues at all. I will say during the winter month's I could not run straight e-85. Started hard on -20f days and took forever to warm up.
 
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