|
|
|
Alcohol and gas mix
After discussing the topic with a friend I noticed that the 90 octane gas that I was putting in my motorcycle gave piss poor mileage. Usually I can easily get 300 mi out of a tank of gas and the tank of 10% alcohol blend was flashing FUEL at only 250 miles. After putting in 91 octane of that same brand but without alcohol I'm back to getting 300+ miles.
I never noticed this in my truck because I burn the cheap 87 octane that has no alcohol. A one tank experiment doesn't answer all the questions but its starting to look like alcohol is mostly a filler if you get 10% less performance with a 10% alcohol mix. Others seem to be noticing the same.
Any thoughts out there?
Dave
|
|
 Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
I suspect it would depend on the engine, but your math is not correct. You are obtaining about 17% less milage with the 10% alcohol.
Alcohol is going to give you less BTU's per gallon just as the winter blend of diesel gives you less BTU's and worse economy. With a 10% mix it should only give you a little less.
Remember that you have 95/5 ethanol to water mix when they distill ethanol as it aziotropes at this ratio. To get higher you must back distill from another solvent like benzene. The alcohol in the fuel will absorb any water in the tanks. Therefore the local fuel retailer gets his tanks cleaned of condensation and you get more than the .5% water you originally had in the gas and considerably less performance. Naturally this applies not only to the local retailer but also to the bulk dealer, pipeline and the tank truck. Do we need a spot test to check for water in the gasoline?
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
Certain greenies push the ethanol blended gasoline as a way to cut emissions as the ethanol burns cleaner. But you do get less fuel mileage so you end up burning more fuel for the same distance negating some of the clean air gain.
Some vehicles react to the ethanol blend more than others. A motorcycle is one that will react more severely than say a car will. My bike is a high performance bike so I won't even consider putting an ethanol blend into it. If you bike is a touch more on the performance end or has been tweaked, then that may account for your more severe reaction to the ethanol blend.
I'm not a scientist and I have done no technical studies to support my hypothesis.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
Well I am a scientist and engineer, but too lazy to look up all the numbers in Perrys etc. I suspect that the higher the compression the worse off you will be. Ethanol will have slightly less BTU value per gallon (76K vs. 116 K BTUs), say 35 percent. At ten percent add ratio that should give maybe a 3.5 % decrease in fuel value per gallon. Naturally the water will decrease the fuel value by another 0.5 %
The ethanol adds oxygen content to the fuel which decreases the formation of hydrocarbons in combustion and other pollutants. It also decreases the temperature of combustion decreasing the level of NOX produced. I am not sure if it is the water or the ethanol that provides this function.
Octane value in a gasoline engine is not just the BTU’s but the suppression of the ignition point, there is very little difference in the BTU value of premium and regular gasoline. The addition of ethanol will decrease the octane rating as it will increase the flash point. Pre-ignition on a high compression engine will decrease the power as on a modern engine the spark timing is automatically decreased to accommodate the lower value fuel on older engines we heard the knock. The higher the compression the more the spark must be retarded and the less value you will obtain from the fuel.
Naturally if the engine is designed to burn the alcohol fuel by itself like a GP car, a top fuel dragster or a Brazilian auto the problems are diminished.
Personally I think to get as large of a decrease as he experienced with his motorcycle engine he was ingesting more than 0.5% water. I have done no technical studies to support my hypothesis, but you do.
This is no longer fun and becoming too much like work, but possibly more informative.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
Thanks Peters. I am an engineer, but too lazy to look up numbers and do the math. I was on assignment for my wife and shouldn't have been looking at the internet at the time I posted my response. So had I been looking up info and been caught...
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
"but your math is not correct. You are obtaining about 17% less milage with the 10% alcohol."
Peters, your answers are starting to sound like Murfs. 
Thanks for the response though. On my fillup this morning I figured the actual mileage for the two tanks: 41.9 mpg on ethanol blend and 47.4 on 91 octane so about 11% or 13% difference depending on the way you calculate it. My compression ratio is pretty high for a modern engine at 10.8:1 (Honda ST1300). I suspected water in the gas as it wanted to sputter a bit when cold. This engine never runs rough so the missing was obvious.
Iowa, What bike do you own?
I know I've used this blend before and it usually seems to run ok. But I've noticed that certain tanks of gas I've burned just didn't give the same mileage. I'm now assuming that these were the fillups with ethanol blend. I might try one more this fall to see if the fuel mileage is reduced.
Dave
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
Maybe that's why our new Highlander is getting much worse mileage than 18/24 that's on the EPA sticker. We're seeing about 15 mpg with 60% highway miles. But our other vehicles haven't changed. Hmmm. Time to take it back to the dealer.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
sounds like you really love that Highlander.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
At 2000 miles I like it about as much as our 86 Corolla. Which isn't saying much.
|
|
Add Photo
Bookmarks: |
|
|
|
|
Alcohol and gas mix
Ken, My 02 Tundra 4x4 gets an honest 17 mpg in mixed driving.
I would think the Highlander would equal or surpass that.
Sometimes it takes 20,000 miles to break in a Toyota engine.
|
|
Add Photo
Bookmarks: |
|
|
|
Gas Generator Weather Protecti
10-17-2005, 17:04 
Digg It 
Del.icio.us 
