It is very easy to make your Avalanche run on E85. You can use a converter like the ones from E85andyou.com. They work with the computer in your truck to make the needed adjustments. If you are worried about all the BS people are throwing around about damage from ethanol, watch this video
http://youtube.com/watch?v=HuOs1yap8mU. It will help clear some things up for you. With use of these kits, fuel economy drops of 5-15% are common. In most areas of the country, E85 runs about 20% less than regular unleaded. E85 is about 105 octane and can reduce emissions by as much as 70%. Performance will NOT suffer. Most see an increase in horsepower. Please think about the corrosive properties of ethanol. It's moonshine.....not battery acid. The oil companies and car manufacturers want you to believe that you need a NEW vehicle.