Venom One
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$50 to fill up?! Damn, I wanna fill up where you do....I just paid $104.90 to fill up today :-(
Flex fuel vs. gasoline
- Thread starter custom99
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$50 to fill up?! Damn, I wanna fill up where you do....I just paid $104.90 to fill up today :-(
custom99
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The higher octane is why I was looking for experiences with it here. A lot of what I was reading on line was that it has higher octane but got less gas mileage. That did not make sense to me. I was hoping to see that people had better luck with it because of the cost difference. I had to use a rental Ford Escape for 3 weeks after
my Yukon was totaled and I needed something until I found this 2003. I used the E85 in that because it was .54 cents a gallon cheaper, but I had no way to know any difference driving something that tiny. I guess I will try a tank of straight E85 and a tank of 50/50 to see what I come up with. I filled the tank when I picked this up and the computer says I have been getting 14.7 so far running gas.
my Yukon was totaled and I needed something until I found this 2003. I used the E85 in that because it was .54 cents a gallon cheaper, but I had no way to know any difference driving something that tiny. I guess I will try a tank of straight E85 and a tank of 50/50 to see what I come up with. I filled the tank when I picked this up and the computer says I have been getting 14.7 so far running gas.
M3PO
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If you have a stock engine and don't have pre-detonation (engine/spark knock) then higher octane wont do anything for you. Octane does not = HP, unless you have something that raises compression, thus requiring your fuel to ignite at a higher temperature.
You will see some guys on here with a custom tune made for higher octane fuel, typically this is a result of the tuner increasing the timing.
As far as E85, I had a '02 Z71, and noticed a significant drop in MPG. I can't remember the numbers, but it was basically a wash, so since at the time there were only a couple of E85 stations, I just stuck with the regular gas/ethanol mix.
You will see some guys on here with a custom tune made for higher octane fuel, typically this is a result of the tuner increasing the timing.
As far as E85, I had a '02 Z71, and noticed a significant drop in MPG. I can't remember the numbers, but it was basically a wash, so since at the time there were only a couple of E85 stations, I just stuck with the regular gas/ethanol mix.
ntxstallion
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Yeah I would not go out of my way to get it. I use it to save a few pennies here and there. I will continue to use it when it is easy to get to.
You have to consider and understand the system, not just one part of it.
Octane is just a measure of the effort needed to combust the fuel... i.e.- how much heat and pressure the fuel can take before it ignites without the aid of the spark plug.
Octane alone will not increase power. It's actually worse to higher octane than necessary since you run the risk of incomplete combustion, causing large amounts of carbon build-up on the piston and combustion chamber (continuously running 93 octane in a 9:1 compression consumer-grade engine will do this, for example).
An engine designed to burn gasoline will have a lower compression ratio than one designed for alcohol fuels. So, burning E85 in an engine designed to also burn gasoline you lose a lot of fuel efficiency. Which is what we are doing with current flex fuel engines.
Take two 5.3 V8s. One at our factory ~9.5:1 compression and another built to 12.5:1 compression. Heads, cam, etc are all kept the same.
If you were to run the 9.5:1 engine on gasoline and the 12.5:1 engine on E85, they would get roughly the same mpg in all driving conditions. However, the 12.5:1 compression engine (running E85) will produce substantially more power as alcohol, while not as energy dense, has a much higher heat of vaporization (~2,400 BTU/gal, versus ~900 BTU/gal for gasoline) which will act as a chemical intercooler as well as a fuel source. The higher compression and cooler (denser) intake charge allows you to extract more net energy from combustion, making up for the smaller energy density (gasoline ~115,000 BTU/gal, E85 ~80,000 BTU/gal).
In conclusion, at this time your only reason to run E85 is if it's economical to do with considering prices in your area. Or if you plan to run a supercharger or turbo, where alcohol fuels shine.
My personal experience for consideration: on the highway, my 07 yukon gets 21mpg on gasoline and 17 on E85 (documented over 50k+ miles). Gas is $3.70/gal here which calculates to 17.6 cents per mile, where as E85 is $3.35/gal which calcs to 19.7 cents per mile. For $3.70/gal gas, E85 would have to be $2.99/gal to break even.
Octane is just a measure of the effort needed to combust the fuel... i.e.- how much heat and pressure the fuel can take before it ignites without the aid of the spark plug.
Octane alone will not increase power. It's actually worse to higher octane than necessary since you run the risk of incomplete combustion, causing large amounts of carbon build-up on the piston and combustion chamber (continuously running 93 octane in a 9:1 compression consumer-grade engine will do this, for example).
An engine designed to burn gasoline will have a lower compression ratio than one designed for alcohol fuels. So, burning E85 in an engine designed to also burn gasoline you lose a lot of fuel efficiency. Which is what we are doing with current flex fuel engines.
Take two 5.3 V8s. One at our factory ~9.5:1 compression and another built to 12.5:1 compression. Heads, cam, etc are all kept the same.
If you were to run the 9.5:1 engine on gasoline and the 12.5:1 engine on E85, they would get roughly the same mpg in all driving conditions. However, the 12.5:1 compression engine (running E85) will produce substantially more power as alcohol, while not as energy dense, has a much higher heat of vaporization (~2,400 BTU/gal, versus ~900 BTU/gal for gasoline) which will act as a chemical intercooler as well as a fuel source. The higher compression and cooler (denser) intake charge allows you to extract more net energy from combustion, making up for the smaller energy density (gasoline ~115,000 BTU/gal, E85 ~80,000 BTU/gal).
In conclusion, at this time your only reason to run E85 is if it's economical to do with considering prices in your area. Or if you plan to run a supercharger or turbo, where alcohol fuels shine.
My personal experience for consideration: on the highway, my 07 yukon gets 21mpg on gasoline and 17 on E85 (documented over 50k+ miles). Gas is $3.70/gal here which calculates to 17.6 cents per mile, where as E85 is $3.35/gal which calcs to 19.7 cents per mile. For $3.70/gal gas, E85 would have to be $2.99/gal to break even.
M3PO
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Nice write up Jay! Much more in depth than mine. I can't blame people for thinking this way, its probably more of a marketing thing, but it drives me crazy when people pay dearly for high octane fuels thinking they are going to get more HP.
Venom One
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Excellent write-up. I won't be running E-85 in my Yukon anymore, but I would like to convert my Cobra to run E-85 as it would greatly benefit from it but from what I understand, it's a bit pricey to do the conversion...
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