Operating system update for e85 compatibility TSB

[Mudsport96]

Knocked down 19.2 mpg running 75-80mph from Peoria il to Davenport ia. Conditions were 72ish degrees and a steady rain. This is on straight 87. Still cant manage to get my wife to use the YELLOW handle to fill the tank, even with the post-it note on the dashboard. However 19.2 at 75-80 is better than the previous long trip i took with the old factory calibration which was 17.9 running 75-80.
If i can ever get a full couple weeks of e85 i will report on that as well

 

[rockola1971]

I only use e85 to clean my fuel system once in awhile. Otherwise its false economy to use it. It literally costs more per mile to drive using e85 vs 87 octane. Science cant be defeated and science shows that ethanol has a lower BTU output than 87 octane. So it takes more of e85 to drive the same amount of mileage using 87 octane. While E85 is cheaper per gallon you simply dont get the same amount of mileage using 87 octane.

 

[S33k3r]

I only use e85 to clean my fuel system once in awhile. Otherwise its false economy to use it. It literally costs more per mile to drive using e85 vs 87 octane. Science cant be defeated and science shows that ethanol has a lower BTU output than 87 octane. So it takes more of e85 to drive the same amount of mileage using 87 octane. While E85 is cheaper per gallon you simply dont get the same amount of mileage using 87 octane.

It just depends on how much cheaper the e85 is than regular. At some point, the e85 may be cheaper. But don't forget to factor the value of your time when you make the extra stops to fuel up, and/or only fueling up at stations with e85.

 

[Mudsport96]

I only use e85 to clean my fuel system once in awhile. Otherwise its false economy to use it. It literally costs more per mile to drive using e85 vs 87 octane. Science cant be defeated and science shows that ethanol has a lower BTU output than 87 octane. So it takes more of e85 to drive the same amount of mileage using 87 octane. While E85 is cheaper per gallon you simply dont get the same amount of mileage using 87 octane.

True i fully believe and know that as someone whom used to use e85 as a "race fuel " . It's been 12 years or better, but if i remember close to right... it took 60 or 65 percent more e85 than c16 to make the same power(1016 hp at the wheels) . We actually ran out of fuel flow at the carb and put a boost referenced nozzle in front of the turbo to help supply fuel.

It just depends on how much cheaper the e85 is than regular. At some point, the e85 may be cheaper. But don't forget to factor the value of your time when you make the extra stops to fuel up, and/or only fueling up at stations with e85.

This is where it comes into play. It is 35 cents cheaper in my town. Almost close enough to call it, if i could use it for a long trip. But short trip driving it doesnt make sense to use.

 

[rockola1971]

It just depends on how much cheaper the e85 is than regular. At some point, the e85 may be cheaper. But don't forget to factor the value of your time when you make the extra stops to fuel up, and/or only fueling up at stations with e85.

And there lies the problem. Ive never seen E85 around here cheap enough that it is actually cheaper to drive on vs 87 Octane. The rough numbers are that you will lose 15-20% fuel economy using E85 vs using 87octane. The engine simply requires more e85 to do the same amount of work it would using 87octane. The proof is laying right in any flex fuel intake manifold. Have a look at the part numbers for say a 2003 Chevy Tahoe 5.3L vin Z (Flex fuel) and you will see the fuel injector part numbers are different from a 2003 non flex fuel 5.3L. Why is that? Because the FFV Injectors are larger and have a higher flow rate to add that extra e85 required to do the same amount of work that 87 octane would do.

 

[swathdiver]

You fellas might consider running a mix for better fuel economy. Mine gets better mpgs with an alcohol content of between 16-20% or so compared with 93 octane gas. I do not ever intentionally burn straight 87 gasoline.

You can see the percentage difference also between burning the differing fuels. It's not as bad as some think.

 

[swathdiver]

Here's where we're at with the Sierra so far:



In this truck, the difference between burning 93 and any mix of Ethanol is even less so far.

 

[Fless]

Here's where we're at with the Sierra so far:

View attachment 345304

In this truck, the difference between burning 93 and any mix of Ethanol is even less so far.

It's really great to see the empirical data for your trucks. Very helpful!

 

[gooffeyguy]

Here's where we're at with the Sierra so far:

View attachment 345304

In this truck, the difference between burning 93 and any mix of Ethanol is even less so far.

You need cheaper E85, lol

 

[Mudsport96]

Here's where we're at with the Sierra so far:

View attachment 345304

In this truck, the difference between burning 93 and any mix of Ethanol is even less so far.

Ive noticed, my old 95 ford even does better on the local 15 percent thats like 89 octane. Now, it shouldn't be possible.. but my untested guess is that at 300k miles it has significant buildup in the chambers. This causes spark knock that i have heard on occasions. Thus the knock sensor pulls timing and mileage suffers. The higher octane resists the knock timing stays optimal and mileage goes back up.