biglg

ZX,
Do you work at a dealership? I notice you tend to answer most posts?

I live in MIssouri where ethanol is available and I would never use it. It may be 20 cents a gallon cheaper but a friend put it in their 07 tahoe one time. It averaged 8mpg. That is BS.

73shark

On the new cars with E85 mileage figures posted, they are about 25%-30% less than the gas figures. Ethanol contains less energy than gas.

ZX1100F1

No I do not work for a dealership, my name is Dave.

If your friend put E85 in his 07 Tahoe and then only got 8mpg something is either wrong with the vehicle or someone is telling a little white fib.

E85 does have less volumetric efficiency than pure gasoline stock (by about 27%) however it has much higher octane (105).
The sensors and software used in the 2007 GMT-900 vehicles are designed to detect the presence of E85 and exploit its higher octane performance potentials by changing the values and parameters of the engine tuning.
The way the truck is designed to perform on E85 (and what we have experienced in hundreds of thousands of miles in tests) is a noticeable improvement in seat-of-the-pants feel (+16hp on the dyno) on E85 with only about a 1mpg Hwy and roughly 2-3mpg City penalty under real world driving conditions.

9.7mpg was the very worst mpg we recorded in any GMT-900 vehicle in tests on E85 and that was on a test track (not towing) with our foot (actually both feet) to the floor in acceleration testing.

The most common problem (complaint is actually more appropriate) associated with the use of E85 fuel is that the engine needs to be cranked for slightly longer than normal before it fires and also may stumble for a few seconds at first light.

In most parts of the U.S E85 is not readily available nor is it cost effective, but now that WalMart has announced its intent to sell E85 at all of its gas stations nationwide we should start to see availability go up and prices come down, in the next few years E85 may become a viable fuel source and those of us with GM built Flex-Fuel compatible vehicles will be ready for it.

kc300c

Another option is to use fishing line. It is stronger than floss.

jasonw75

Dave:

Can you mix half and half? What if I have a half tank of gas and pass an E85 station, can I top if off? Or should it be all E85 or all gasonline?

Jason

biglg

I am wanting to know the answer to the above question also. Thanks.

jasonw75

Dave:

Would I be better off using E85 when towing?

Jason

ZX1100F1

You are OK to use either straight gasoline or E85 or any mixture of both, the system is capable of detecting any amount of Ethanol and making the necessary adjustments.

Due to the high octane (105) E85 is very good (power wise) for towing but you will experience a reduction in range that may be objectionable depending on how far away the boat ramp is.

jasonw75

Dave:

I live in Michigan and drive to Wyoming twice a year towing a 5,000 LB trailer with 5 sleds in it. It is around 3,000 Miles round trip. If the E85 is more powerful, wouldn't it use less of it through the mountains because I don't have to be as far into the pedal?

Jason

ZX1100F1

You would certainly think that E85 would give you better mileage but it doesn't, the fuel has less energy potential.
I’m not a chemist so I can’t explain it with more detail.

The best thing to do is to try a few full tanks of E85 and see how well it performs based on your driving style.

What the engineers at GM have attempted to do is provide a seamless driving experience regardless of which fuel that you have in the tank by taking advantage of the beneficial performance properties that each fuel offers.