Useless Information

[Kenny D]

I'll trade ya my 3.08 for your 3.73.

 

[HiHoeSilver]

I'll see that 3.08 and raise you a 3.42

 

[swathdiver]

Considering his 6-speed/3.08 to my 4-speed/3.73, I'll accept my 1 MPG deficit.

The tune didn't do anything but disable AFM, speed limiter and rear O2s and tweak some of the transmission stuff a little. No fuel/timing/performance tweaks were made (unless you count removing some Torque Management as performance). I lost about a half mile per gallon since disabling AFM. More recently, I filled up with 89 octane from Chevron the tank before last and Jenn filled up since that one with 87 octane from Murphy USA (Walmart). When we were in it this afternoon, only about 1/8 tank had been burned of the Murphy 87 and the average was at 16.4. So, just running 89 octane more than compensated for the loss from no AFM...

Forgot that yours is a 4-speed, both are awesome with regards to fuel economy. I would say they are more efficient than those little cars because of what we can do with our and how long they last.

I bet you'll pick up 2 mpg by switching to a top tier 93 like Mobil. E85 pumps have yellow handles and many Racetrac stations have them and are less common at Sunoco.

 

[iamdub]

Forgot that yours is a 4-speed, both are awesome with regards to fuel economy. I would say they are more efficient than those little cars because of what we can do with our and how long they last.

I bet you'll pick up 2 mpg by switching to a top tier 93 like Mobil. E85 pumps have yellow handles and many Racetrac stations have them and are less common at Sunoco.

Even if I got 2 MPG better, the cost of 93 severely outweighs that gain. I wanna try E85 when we're off this trip. I'm sure it'll be fine, but I've never ran more than E10 and I doubt the previous owner did since it's so rare in Louisiana. I did find a map of the E85 stations and will hit up one of them back home. It'd be great if the E85 matched or beat the E10 or E0 MPG.

 

[kbuskill]

It'd be great if the E85 matched or beat the E10 or E0 MPG.

Don't hold your breath, or mine either for that matter. E85 will give you absolutely horrible MPG. I don't see any benefit from an economic stand point. Performance maybe but not miles per gallon.

 

[swathdiver]

E85 will not increase your MPG, they will definitely go down. If E85 is low enough in price, it may be more economical to run than regular gasoline. Did a 120 mile or so run tonight and the truck averaged 14 mpg on the highway with E85 @ 62% alcohol content. That's what the 2010 Yukon XL 4x4s were rated for so right on par. It costs me .25 cents a mile to run my truck on 93 or about .18 cents a mile on E85 at the current prices.

Your 2008 2WD Tahoe was rated for 14 City / 20 HWY on gas and 11 City / 15 HWY on E85.

 

[iamdub]

Ugh. I thought it would get the same or better MPG. That's fine, it keeps me from going outta my way to try it. Thanks for the forewarning.

 

[Tonyrodz]

E85 will not increase your MPG, they will definitely go down. If E85 is low enough in price, it may be more economical to run than regular gasoline. Did a 120 mile or so run tonight and the truck averaged 14 mpg on the highway with E85 @ 62% alcohol content. That's what the 2010 Yukon XL 4x4s were rated for so right on par. It costs me .25 cents a mile to run my truck on 93 or about .18 cents a mile on E85 at the current prices.

Your 2008 2WD Tahoe was rated for 14 City / 20 HWY on gas and 11 City / 15 HWY on E85.

Can gas and e85 be mixed? If you have a 1/2 or 1/4 tank of either, and fill up on the other, will it hurt anything?

 

[swathdiver]

Can gas and e85 be mixed? If you have a 1/2 or 1/4 tank of either, and fill up on the other, will it hurt anything?

Sure can but "they" say its best to run one or the other. Mine runs pretty good at 30% ethanol and that's usually when switching over from gas to ethanol. The mileage is certainly better and the motor loves the higher alcohol content.

Like I said earlier Chris, if the price is low enough, it makes sense to use it, or if you want to romp on it on a cool night at the track! Then who cares about mileage.

After using six or so of those little bottles from walmart, my mileage has increased some, cleaner injectors I reckon. My buddy uses those same ones in his Duramax. i have some more in the back, should toss one in with this tank of E85 and see how it goes.

Merry Christmas fellas!

 

[Fless]

E85 will not increase your MPG, they will definitely go down. If E85 is low enough in price, it may be more economical to run than regular gasoline.

Agree with the less MPG. But unless something has changed, when running E-85 GM recommends a mix of E-85 and gasoline. From my '04 manual:

To insure quick starts in the wintertime, the E-85 fuel must be formulated properly for your climate according to ASTM specification D 5798. If you have trouble starting on E-85, it may be because your E-85 fuel is not properly formulated for your climate. If this happens, switching to gasoline or adding gasoline to your fuel tank may improve starting. Your vehicle is designed to accommodate a mixture of gasoline and E-85 fuel. For good starting and heater efficiency below 32°F (0°C), the fuel mix in the fuel tank should contain no more than 70% ethanol.

E-85 has less energy per gallon than gasoline, so you will need to refill your fuel tank more often when using E-85 than when you are using gasoline. Regular unleaded gasoline is recommended when pulling a trailer. For payload capacity with ethanol fuel, see Loading Your Vehicle on page 4-58.

Notice: Some additives are not compatible with E-85 fuel and may harm your fuel system. Damage caused by additives would not be covered by your new vehicle warranty. Do not use additives with E-85 fuel.
​

I've run it both ways, all E-85 and a mix, but experienced hard starting in cold temps with mostly E-85. Around here (Denver) we almost never get 85% ethanol in E-85, and the only place I've seen it available is Western Convenience. Also kinda wondering what specific additives would be incompatible.