I just returned from a 3700 mile drive from Ohio to Colorado and back.  My truck is a 2002 Chevy 2500HD with a 6.0 GAS engine and a Procharger supercharger and about 500HP.  We took our 4 horse trailer with 10' LQ and a Jeep back in the horse area.   The Jeep now thinks it is a horse but that is another story.  Trailer weighs in at about 11,500lbs full of stuff, over weight for a 6.0 but well under for the same truck with an 8.1 or 6.6. 

On our pull west in NE, up hill we got between 11 and 13 mpg as reported by the Scan Gauge II.  Just north of Denver we stopped and got ethanol blended fuel.  My 500HP dropped by a lot.  On the freeway in Denver the truck would not hold overdrive and the tranny temp kept climbing as did the water temp.  We put the windows down and ran the heat to keep the engine cool and it worked.  We limped along like that getting only 5-7 mpg till that tank ran dry in Canon City.  There I put in 12 gallons of Ohio gas so we could climb the hill and make our way to Leadville.  With the non-blended fuel the temps came down and the truck had power again.  Then the time came to go home and I added some blended fuel and the problem reappeared but I was ready for it with octaine booster that had no alcohol.  I also increased to fuel pressure so the lean burn would not bring the temps up so high but I was already near the limit of the adjustment but it did help some. 

In IL on I70 we got our first non-blended fuel for the drive home and the mileage slowly came back up to 12 mpg once we got gas for the last time.  Blended fuel doubled my fuel consumption and increased engine and tranny temps along with a drastic reduction of power. 

Jeeppler

Have you tried a synthetic automotive transmission fluid? Using my stock OEM coolers, the synthetic dropped my indicated temps to where it is not a concern, regardless of the hills or loads. Just a thought.

I can see where these bio fuels are going to make us foreign energy independent. You get less power, so you use more of it. Of course this is what happens whenever the government gets involved.

Gard

Why would the blended fuel have ANY effect on your transmission temps?

I could believe that blended fuels may give you worse mpg. But the fact that you had worse mileage and increased trany temps suggest that there were other external factors. Such as head winds, elevation, grades of climb, outside air temps. Sounds like your truck was working harder. I don't doubt you, just curious

Many transmission oil coolers share the same water in the radiators with the engines. As the engine heats up, the water temp increases, and the trans oil temp will raise as a result. Manufacturers use this system to ensure proper transmission oil temps, and faster warm ups, with low ambient temperatures.

When his engine lost power, the transmission kicked out of OD which unlocks the torque converter, to maintain the engine rpm. With the torque converter unlocked and slipping, the tranmission oil is subject to a shearing action, which increases its opperating temperature.

A stand alone cooler or an after market add on cooler in series in the fluid return line, can lower the transmission oil temperatures lower than the radiator water temp. However, without an internal thermostat, it can result in overcooling during winter months.

His engine is using a blower which is a large heat pump. Depending on if an inlet inter cooler is being used, it is very easy for the driver to over tax his original cooling system. With a bio fuel giving less power while effectively leaning the mixture, the driver has to apply more throttle, adding more heat to the motor, and adding even more of a cooling problem, to an already overtaxed system.

Gard

Gard hit it on the head.  When the engine lost power the tranny unlocked the torque converter, the tranny temps started to climb right after I put the bio fuel in the tank.  The water temp started up because the supercharger was pressurizing the intake, the injectors added fuel at the rate for normal gasoline.  As I added more throttle  it made the engine run leaner and leaner.  E85 should run 11:1, 11 parts air and 1 part fuel, gasoline is 14.7:1 and that is the rate the computer added fuel.  A lean engine run very hot, the supercharger allowed the engine to add a lot of air but the needed fuel was not being added because my computer cannot understand it needs to add more fuel because it is an alcohol mixture.  The blower added more air as the throttle was pushed down but not enough fuel was added and the cycle got to the point the radiator was over taxed. 

I run Mobile One in everything, oil, tranny and diffs all have Mobile One.  I have an intercooler, the intake temp was never above ambient plus 20, it did not help that it was over 100 degrees outside to start with but intake temps of 120 are not too bad.

The thing that shocked me was once I added the fuel we brought with us the power returned and the temps went down.  On our way out with the blended fuel the temps went right back up and power was gone. 

I use the same Mobile products in everything I own and have never regretted it.

Question: Did the usage of the octane booster, effect in any way, the overall lower qualities of the bio fuel? Was it worth the trouble? I was considering the purchase of some to keep in my cars, whenever I was confronted with the bio fuels at the pump. I don't know if it would be a waste of time and money or not. On my GM v6 automobiles, it costs me about 4 mpg to use the bio fuel.

Sounds as if you have quite a set up on your truck and you're very knowledgeable with its operation. It's too bad that it is so dependent on proper fuels, and that the new ones degrade its performance so badly.

Gard

The octane boost helped.  We put it in when we got bio blend fuel in Salida and had to climb over Poncha Pass.  The truck had more power than it had on just the bio blend fuel but not as good as it has on pure gasoline.  I doubt you will recover the cost of the non alcohol octane boost by adding it to a bio blend fuel, but it would be interesting to see what kind of change in mileage you would get doing that.

When we move west or bio blend fuel is everywhere, I will have to put larger injectors in my truck so I can throw more fuel and still keep the computer happy.