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Octane rating or ethanol. Which is more

14K views 45 replies 12 participants last post by  32vld 
#1 ·
important? My dealer has told me to use 89 octane gas in my mower and handhelds. On the other hand, I can get ethanol free gas in 87 octane. Would the ethanol free/lower octane be better to run? Thanks
 
#2 ·
89 in handhelds and 87 in mowers is fine...

That being said, I have not experienced but one problem that I could even relate to ethanol...I think sometimes its used as a thing to blame for crap equipment and poor mechanic work...I'm not saying this is the case all of the time.
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#4 ·
ethanol can and has been proven to be harder on seals and stuff in fuel systems of vehicles. it can eat certain rubbers pretty quickly. newer ones are designed with this in mind but older engines can have problems related to it. it's pretty standard around here to have at least 10% ethanol. the other issue i have with ethanol is there is less energy per gallon than straight gasoline, so you need more ethanol to make the same power. this translates to lower fuel mileage. granted at 10% its not a huge difference but it's still there all the same.
 
#5 ·
ethanol can and has been proven to be harder on seals and stuff in fuel systems of vehicles. it can eat certain rubbers pretty quickly. newer ones are designed with this in mind but older engines can have problems related to it. it's pretty standard around here to have at least 10% ethanol. the other issue i have with ethanol is there is less energy per gallon than straight gasoline, so you need more ethanol to make the same power. this translates to lower fuel mileage. granted at 10% its not a huge difference but it's still there all the same.
You've opened a can of worms now! I've said ethanol produces less energy on here before and was ridiculed.
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#6 ·
Ethanol has less carbon per pound versus petroleum because of the oxygen in its molecule. The lower percentage of carbon is why there are fewer BTUs, therefore less energy released when it is burned or used in an engine. That oxygen in its molecule is what contributes to its corrosive properties above and beyond what is caused by its tendency to absorb water. In terms of fuel value: ethanol<gasoline<biodiesel<diesel.
 
#8 ·
another thing i don't understand is why diesel is more expensive now, it's a less refined ''dirtier'' product
No joke...it's because we depend on it so much for transportation of food.
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#12 · (Edited)
To just say gasoline has more energy per gallon and then walk away leaves out a lot of important information.

If gasoline is the more powerful fuel then when are the alcohol and nitromethane users going to start losing races to gasoline running cars instead of having the fastest times?

Gasoline A/F ratio is 14.7:1.

Gasoline engines need 14.7 parts of air to burn all of that 1 part of gas up during combustion. Putting in more fuel will just be wasting it.

Alcohol has less energy though more fuel gets into each cylinder. Because it needs less air to completely burn so some of the air's volume is replaced with fuel. A/F ratio is around 6:1 with alcohol.

That means that alcohol fueled engines get 2.45 more times the fuel into the cylinder.

Alcohol has 2/3 the energy of gasoline. But 2.45 times more alcohol gets into the cylinder. So multiply .667 x 2.45 = 1.63 more energy.

Alcohol fuel has it's advantages and disadvantages. Where I live you only can buy 10% blend alcohol and gas at the pump.

When manufacturers refuse to build there equipment to be able to run with alcohol blended fuels they are refusing to face reality and giving their customers a big FU with every piece of equipment that they sell to their customers, or should replace the words sell to their customers with stick it to their customers.

Years ago when alcohol was introduced into gas by federal mandate I was a GM dealer mechanic. At the factory GM school their instructor said that GM told the gov. that it's cars can run on alcohol up to 10%.
That the ethanol should be the alcohol of choice. It is less harmful to the cars parts.

That methanol would need to be run at a 5% blend and would be more harmful to the cars parts.

Well our elected representatives in the capital let the methanol lobbist's buy their votes instead of listening to the automotive manufacturing experts.

So we had more alcohol related problems as a result. Then as happens eventually station tanks leak and the MTBE, which the added methanol was named began to poison our waters. This is when the Fed Gov prohibited MTBE as a fuel additive with replaced it with ethanol.

Common sense is when engine manufactures say ethanol is a better fuel additive then methanol. When ethanol is non poisonous (it is in our favorite adult beverages) so if it was to leak into the ground waters the environment would not be harmed. That methanol/MTBE use as a fuel additive would of been rejected by both houses of congress.

The question that needs to be asked: Why does the American public continually vote in people that are that dumb, that corrupt, or both, every election?

Maybe congress feared an ethanol shortage and the end of the three martini lunches, and all business in Washington DC would come to a stand still for they would not have the fuel and lubrication so necessary to govern.
 
#13 ·
Tell me about it. It makes absolutely no sense.
Diesel cost more becuse we are exporting all excess supplies and the balance for domestic consumption pays the difference. Just returned from the UK on a business trip Two weeks ago and Diesel was $9.00 per gal. If anyone wants to complain abouit the fuel cost here in the US, you and everyone else have no idea how good you have it.
easy-lift guy
 
#14 ·
To just say gasoline has more energy per gallon and then walk away leaves out a lot of important information.

If gasoline is the more powerful fuel then when are the alcohol and nitromethane users going to start losing races to gasoline running cars instead of having the fastest times?

Gasoline A/F ratio is 14.7:1.

Gasoline engines need 14.7 parts of air to burn all of that 1 part of gas up during combustion. Putting in more fuel will just be wasting it.

Alcohol has less energy though more fuel gets into each cylinder. Because it needs less air to completely burn so some of the air's volume is replaced with fuel. A/F ratio is around 6:1 with alcohol.

That means that alcohol fueled engines get 2.45 more times the fuel into the cylinder.

Alcohol has 2/3 the energy of gasoline. But 2.45 times more alcohol gets into the cylinder. So multiply .667 x 2.45 = 1.63 more energy.

Alcohol fuel has it's advantages and disadvantages. Where I live you only can buy 10% blend alcohol and gas at the pump.

When manufacturers refuse to build there equipment to be able to run with alcohol blended fuels they are refusing to face reality and giving their customers a big FU with every piece of equipment that they sell to their customers, or should replace the words sell to their customers with stick it to their customers.

Years ago when alcohol was introduced into gas by federal mandate I was a GM dealer mechanic. At the factory GM school their instructor said that GM told the gov. that it's cars can run on alcohol up to 10%.
That the ethanol should be the alcohol of choice. It is less harmful to the cars parts.

That methanol would need to be run at a 5% blend and would be more harmful to the cars parts.

Well our elected representatives in the capital let the methanol lobbist's buy their votes instead of listening to the automotive manufacturing experts.

So we had more alcohol related problems as a result. Then as happens eventually station tanks leak and the MTBE, which the added methanol was named began to poison our waters. This is when the Fed Gov prohibited MTBE as a fuel additive with replaced it with ethanol.

Common sense is when engine manufactures say ethanol is a better fuel additive then methanol. When ethanol is non poisonous (it is in our favorite adult beverages) so if it was to leak into the ground waters the environment would not be harmed. That methanol/MTBE use as a fuel additive would of been rejected by both houses of congress.

The question that needs to be asked: Why does the American public continually vote in people that are that dumb, that corrupt, or both, every election?

Maybe congress feared an ethanol shortage and the end of the three martini lunches, and all business in Washington DC would come to a stand still for they would not have the fuel and lubrication so necessary to govern.
You backed my statement. Pound for pound, less energy. It takes more alcohol to equal the same btu as gasoline. And unless the engine is designed to run on alcohol the performance vs gasoline will be less.
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#15 ·
Two equal compression engines, one running ethanol and one gas. The gas engine would produce more power...can't be argued, goes against physics.

Change the compression ratio which adds more air to the combustion process allowing the lower energy, but higher octane alcohol to produce more power.
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#16 ·
And once again...everyone brings out race cars using alcohol vs gasoline.

Your daily driver is not a race car, a race engine or a high compression engine...nor is your "designed for 87 octane" mower or trimmer.
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#17 ·
alcohol also has a higher octane rating, and the extra fuel also equates to some extra cylinder cooling. Yes, when you are talking full on race engine alcohol has plenty of advantages. that makes up a very small portion of engines out there, and they aren't on the road. even with the 10% ethanol being sold in pumps now there IS a mileage drop, and with the drought we had this year i doubt ethanol has much savings at all. If you compare e85 to gasoline i don't believe there is any cost savings. E85 is only at max 40-50 cents cheaper around here. I get 17mpg on gasoline and i've heard i'd get maybe 11-12 with e85.

today gasoline was 3.65 at quiktrip. that is 22 cents per mile at 17mpg for me.
E85 is 3.20. that is 27 cents per mile at 12mpg. for me, it's actually MORE expensive to use e85
 
#18 · (Edited)
Two equal compression engines, one running ethanol and one gas. The gas engine would produce more power...can't be argued, goes against physics.

Change the compression ratio which adds more air to the combustion process allowing the lower energy, but higher octane alcohol to produce more power.
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Changing compression ratio does not change the amount of air that a naturally aspirated engine can draw in.

Alcohol engines do not produce more power because they run at a higher compression. They produce more power because more fuel gets into the cylinder. Lower energy fuel is put in quantity greater, 2.45 times more fuel, enough greater volume of fuel that more power is produced.
 
#19 · (Edited)
Changing compression ratio does not change the amount of air that a naturally aspirated engine can draw in.

Alcohol engines do not produce more power because they run at a higher compression. They produce more power because more fuel gets into the cylinder. Lower energy fuel is put in quantity greater, 2.45 times more fuel, enough greater volume of fuel that more power is produced.
My analogy on compression ratio was described wrong.

Please explain to me how more fuel would get into the cylinder of a stock engine running alcohol vs gasoline. Both equal engines, same carbs same everything.

When I ran karts the carb jets were drilled larger for alcohol but no power gains were achieved from running alcohol. Dyno testing proved this. Same engines, same carbs...change one jet to run alcohol, now change the jet to run gas...same power.

Now try to run the alcohol engine on gasoline or vice versa and they would not run properly if at all.
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#20 ·
If you are going to put the same amount of fuel is one thing.

The advantage of why you can use alcohol to get more power is because you can put more fuel in a cylinder and it will completely burn. Where extra gasoline won't get burnt and will go out the tail pipe.

Why do alcohol dragsters go faster?

Is it because alcohol weighs less then gas so the weight reduction makes them faster?

Or is it they can get more power out of alcohol?

Yes different fuels have different btu producing ability. That fact alone is misleading because ignores what can be done in the real world.
 
#21 ·
To answer the original question, all 2 stroke manufacturers tell you not to use lower than 89 octane. I don't know of any 4 stroke manufacturers that tell you that. So unfortunately if all you have in E0 (ethanol free) is 87 you are stuck with using E10 89 octane in your 2 strokes. I see no problems and only advantages to using the E0 87 octane in your 4 stroke stuff.
 
#22 ·
Incidentally they are trying to push through the requirement for E15 (15% ethanol) even though any more that 10% is prohibited by all small engine manufacturers and will harm many other equipment and older cars. Both will likely be available from the same pump which will lead to huge misfueling problems from people not knowing what their car can run on. The government has even come up with the stupid idea that where both E10 and E15 are available from the same hose and pump that there be a 4 gal minimum purchase of E10 just to purge the pump and hose of E15 to make sure the ethanol content of the E10 is not greater than 10%.
 
#23 · (Edited)
If you are going to put the same amount of fuel is one thing.

The advantage of why you can use alcohol to get more power is because you can put more fuel in a cylinder and it will completely burn. Where extra gasoline won't get burnt and will go out the tail pipe.

Why do alcohol dragsters go faster?

Is it because alcohol weighs less then gas so the weight reduction makes them faster?

Or is it they can get more power out of alcohol?

Yes different fuels have different btu producing ability. That fact alone is misleading because ignores what can be done in the real world.
Alcohol dragsters go faster because the engines are built for alcohol, but once again...we are talking mower and trimmer engines, not supercharged high compression engines DESIGNED to run on ALL alcohol.

Btus are still btus...in order to make more power out of less btus something has to change internally inside an engine...so they increase the compression ration and install superchargers that can utilize the higher octane ethanol, though lower btu and in turn they overcome the lower btu output of the fuel.
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#24 ·
This has been talked about before. Yes ethanol has less BTU's than gas but has more energy density. Higher ethanol produces more HP. Below are the results from many studies done to prove this. Sorry its hard to read because the chart doesnt copy and paste just the text. Ethanol content is the second line down and HP is second from bottom. Results are listed in order from E10 up to E85.


Table 4. Heavy-Load (4.7 L Engine)
Fuel Ethanol Content 10% 20% 30% 85%
BTU content (BTU/gal) 111,070 107,140 103,210 81,595
% change in BTU’s per gallon 0% -3.5% -7.1% -26.5%
65 mph
Hp 50.8 52.1 52.0 54.4
Gph 5.96 6.08 6.27 6.93
Mpg 10.7 10.5 10.3 9.3
BTU’s per mile 10,347 10,237 10,016 8,744
Gallons per hp hr 0.117 0.117 0.120 0.127
BTU per hp hr 13,035 12,514 12,431 10,393
Fuel Trim % -2.6% -1.0% -1.4% -0.6%
Injector Pulse Width (ms) 8.5 8.6 9.1 11.6
% change in pulse width 0% 0% 7% 36%
50 mph
Hp 34.5 33.0 40.4 33.3
Gph 3.81 3.91 4.01 4.51
Mpg 13.1 12.8 13.1 11.1
BTU’s per mile 8,459 8,348 7,908 7,338
Gallons per hp hr 0.110 0.118 0.099 0.135
BTU per hp hr 12,271 12,678 10,253 11,043
Test Cycle
Mpg 12.7 12.4 12.2 10.9
% change in mpg 0% -2% -4% -14%
BTU’s per mile 8,738 8,348 7,908 7,338
% change in BTU’s per mile 0% -1% -3% -14%
Cost per mile $0.193 $0.196 $0.198 $0.183
% change in cost per mile 0% 1.6% 2.6% -5.2%
Other
Max hp (2nd gear) 195 197 198 202
Max torque (2nd gear) 235 241 240 247
 
#25 ·
This has been talked about before. Yes ethanol has less BTU's than gas but has more energy density. Higher ethanol produces more HP. Below are the results from many studies done to prove this. Sorry its hard to read because the chart doesnt copy and paste just the text. Ethanol content is the second line down and HP is second from bottom. Results are listed in order from E10 up to E85.

Table 4. Heavy-Load (4.7 L Engine)
Fuel Ethanol Content 10% 20% 30% 85%
BTU content (BTU/gal) 111,070 107,140 103,210 81,595
% change in BTU’s per gallon 0% -3.5% -7.1% -26.5%
65 mph
Hp 50.8 52.1 52.0 54.4
Gph 5.96 6.08 6.27 6.93
Mpg 10.7 10.5 10.3 9.3
BTU’s per mile 10,347 10,237 10,016 8,744
Gallons per hp hr 0.117 0.117 0.120 0.127
BTU per hp hr 13,035 12,514 12,431 10,393
Fuel Trim % -2.6% -1.0% -1.4% -0.6%
Injector Pulse Width (ms) 8.5 8.6 9.1 11.6
% change in pulse width 0% 0% 7% 36%
50 mph
Hp 34.5 33.0 40.4 33.3
Gph 3.81 3.91 4.01 4.51
Mpg 13.1 12.8 13.1 11.1
BTU’s per mile 8,459 8,348 7,908 7,338
Gallons per hp hr 0.110 0.118 0.099 0.135
BTU per hp hr 12,271 12,678 10,253 11,043
Test Cycle
Mpg 12.7 12.4 12.2 10.9
% change in mpg 0% -2% -4% -14%
BTU’s per mile 8,738 8,348 7,908 7,338
% change in BTU’s per mile 0% -1% -3% -14%
Cost per mile $0.193 $0.196 $0.198 $0.183
% change in cost per mile 0% 1.6% 2.6% -5.2%
Other
Max hp (2nd gear) 195 197 198 202
Max torque (2nd gear) 235 241 240 247
This is an engine designed to run on either fuel and would naturally have ways to ret@ard timing when using straight gas to prevent preignition. Engine is tuned to generally run e85.
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#26 ·
This is an engine designed to run on either fuel and would naturally have ways to ret@ard timing when using straight gas to prevent preignition. Engine is tuned to generally run e85.
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These results are from a stock 2005 Dodge Ram with 4.7L Magnum. Test was also done on three other vehicles with similar results but I didnt want to copy and paste a bunch of the same stuff(I can if you want). Final conclusion was less BTU's per horsepower are needed with higher ethanol but more fuel was burned droping MPG. This was a HP and MPG study.
 
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