Last year I was using regular unleaded 87oct gas and had a steady 18 mpg on every tank. On trips I got 19-20 mpg, now I have been using 89oct (with ethnoal) and gas mpg dropped to 16mpg! Could the higher octane gas give me lower gas mileage? I used the 89oct because it was a nickel a gallon cheaper. The only thing I have done to the p/u is change the fuel filter. The wife's car is doing the same thing. I have not used the same gas station all the time, nor has the wife. Anybody help?

 

Its the ethonal.

Every time I use that blended crap my milage drops.

Just stick with the 87 octane. Personally I dont like putting Ethonal in my tank for 2 reasons.

1. I seem to suffer a 10% drop in fuel economy

2. I dont like putting alcohol into my fuel tank.

 

^^^^^
What he said. The octane has nothing to do with your MPG loss. It is all in the lower energy content of the ethanol. Go back to 87. 89 is a waste of money in these trucks.

 

Cheaper than 87 ???

 

I guess I did not read that part of his post. It could be cheaper being part ethanol. I think I saw somebody post a while back that ethanol has gotten cheaper, so it is possible for it to be cheaper. But if you are getting that much worse gas mileage, then a nickel a gallon cheaper is still wasting money.

 

Saw a couple of station sign pictures since the prices have gone through the roof that had ethanol blends quite a bit cheaper per gallon than the regular stuff.

So far as I know or have seen, nobody in this part of the country even offers a blended gas anymore.

 

It takes twice as much ethonal to do the same work as gasoline!

 

I dont like putting alcohol in my fuel tank either, rather put it in my stomach, just my .02

 

In one of my undergrad classes we have been dealing with alot of conversions with ethanol blends. First of all, octane rating has nothing to do with energy content, it is simply an anti-knocking agent. All gasoline has an energy content of no more than 124,000 Btu/gal. Diesel is 140,000 Btu/gal and ethanol is 76,000 Btu/gal. So heres the math:

10% ethanol blend = .10 x 76,000 Btu = 7600 Btu
+ .90 x 124,000 Btu = 111, 600 Btu
Total Btu of blend = 7600 + 111,600 = 119,200 Btu

So as you can see the energy content is nearly 5% less per gallon, so you can expect mpg decreases of atleast 5% also. Ethanol is the way of the future though. The worlds proven oil supplies our rapidly decreasing. I think in the near future we will see more engines speciically designed for ethanol and hopefully will get better mileage.

 

i dont mean to argue b/c i am probably wrong, but i thought ethanol was supposed to burn allot hotter that gas, giving it more power

 

Ethanol burns cleaner in terms of Nox emissions and such. But in terms of potential energy it contains 76,000 Btu compared to Gasolines 124,000 Btu(This is a max, average gasoline is about 115,000 Btu). It takes about 1.5 - 1.6 times the amount of ethanol to do the same work as gasoline, thats why fuel mileage with blends is slightly less. This can not be changed, its a fact. Ethanol is much better for the environment because of the reduced emissions from the cleaner burn. Thats why the future is in ethanol in my opinion. Not to mention we could help American farmers and reduce our dependency on OPEC,

 

Well put ksuroper. Ahh I remember the days of thermo... Stupid prof. put a gas engine on the final.