I just bought a new Sierra 1500 with the 5.3 flex-fuel engine. Does anyone here have any experinnce with this engine and fuel. Any info would be appreciated.

i heard u get aprrox. 10 mpg better with the e85 fuel

My understanding is that your mileage worsens, but the cost per gallon reduction more than offsets the efficiency loss.

That engine allows you to run on low octane gas as well as E85.

Your engine is designed to operate on 87 octane gasoline. The E85 rating allows you to use fuel with up to 85% ethanol alcohol and this fuel should only be used in vehicles designed for it. Don't look for improved fuel economy, but hopefully the fuel will be priced right! The nice thing is that the fuel is an easily renewable energy source. Many stations will not have E85 available. Do not use a fuel with more than 85% ethanol and this percentage should be on a label at the station selling it. To assure quick starts in the wintertime, the E85 fuel must be formulated properly for your climate according to ASTM spec D 5798. If you have trouble starting on E85, it may be because you fuel is not properly formulated for your climate. Switching to gasoline or just adding some gasoline may help. For good starting and heater efficiency below 32 degrees F, the fuel mix in the tank should be no more than 70% ethanol. E85 has less energy per gallon than gasoline so you will need to refill your fuel tank more often when using E85 than when you are using gasoline.

Ok. If I pull into a station with, say, 1/4 of a tank of "normal" gasoline -- is it ok to fill 'er up with E85? (And vice versa, of course)

Does anyone know if it's a good idea/bad idea/completely forbidden to mix the two types of fuel?

Gracias.

You can mix the fuels. There is a sensor that samples the fuel so the engine management system knows what percentage of ethanol you are using. I think the owners manual recommends the vehicle be driven a short distance after mixing the fuel to allow the system to properly adjust to the current mix, check your manual.

Hey Stingray4, I think you need to see this product. This product re-formulate the fuel (gasoline, ethanol, etc), to "bridge the lubrication gap" and bring to your engine more MPG and more power. Check it out.
http://www.4-corp.com/gmartinez

email me if you have any question..

SLJ2137694 --

Many thanks.

See the October issue of Consumer Report about THE ETHANOL MYTH. The true cost and mileage. Will it really solve America's energy problems? Check it out.