dre23

Yeah, I've heard that the octane level of E85 is pretty high up there. Just to be clear though, cuz I've had other peeps try and fuss me down, the "85" in E85 has nothing to do w/its octane level, correct?

By the way, just filled my first tank w/E85 last week (couldn't resist the $2.79 price tag versus the $3.13 for reg.!) and will have to do some more test runs to see how the truck runs, i.e. if it does indeed run better, but it def does seem to go thru the tank more quickly, that's for sure, so it is a def tradeoff.

wde3477

Yes, E85 means that the mix is a target 85% ethanol and 15% unleaded gas, with some tweaking of percentages done for winter blends and such.

It's my understanding there's also an 'M' series blend, where methanol (the alcohol that will make you go blind!) is used, but it's not in widespread use, and I'm not sure that it would be recommended for unmodified motor vehicles.

From http://www.agriculture.state.ia.us/e85q&a.html
What is the octane rating of E85 compared to gasoline?
Regular unleaded gasoline has an octane rating of 87; E85 has an octane rating ranging from 100-105 making it a high performance fuel. Ford FFVs produce a 5% horsepower gain when using E85.

onall4x4

i was talking to a to a ford tech and he said that e85 dosent burn as hot like reg gas.so you wont get the gas milage as you would with reg gas.but what it does do is put less emissions in the air,and thats what there going for.so he told me.im going to ask around yet.

wde3477

heheh - OK, I can't resist.

I think that 'burns as hot' needs more clarification. Alcohol has a higher octane than gasoline - meaning more or less that it takes a higher level of heat to ignite it. Alcohol also has a lower heat content per volume - meaning there are fewer available BTUs of heat per gallon. Heat is what makes an internal combustion engine 'go'. I'm not aware of any data available for the peak combustion temperatures between alcohol and gasoline.

From: http://www.eia.doe.gov/kids/energyfa...alculator.html
1 gallon of gasoline = 124,000 Btu
1 gallon of diesel fuel = 139,000 Btu
yet we know that a diesel truck will get more than a 12% improvement in mileage, based only on the BTU ratios of the fuels. The other component in fuel efficiency is engine compression. By the accounts I've read, a straight alcohol engine should be able to run with a compression ratio in the 12:1 range, given its higher 'octane' number. Also by the accounts I've read, ethanol has about 76,000 BTU of heat per gallon.

But FFV vehicles have to be a one-engine-fits-all fuels situation. Suggest that if engines were made available, specifically tuned to run only E85, the mileage difference would not be so great as compared to regular unleaded gas engines.

So, I think ethanol can be a part of the energy/environment solution, but not in the p*ss-poor manner of blending various proportions for use in neutered engines set up to burn any combination thrown at them.

NGM

If you are gonna drive it use regular fuel.. The E-85 does have a higher octane rating.. I thought it was like 114 or 110.. Be that as it may. They are correct that the fuel mileage is worse with it. If the engine is not tuned to run it you can damage your engine.