That's right. Fuels with ethanol don't deliver the same gas mileage. The difference is not that much though. Ethanol raises the octane level also. All the regular and mid grade gas around my area has up to 10% ethanol. I think the premium may be ethanol free but if we pay for premium gas to get 3% better fuel economy I think we'd be spending more. I'd say you're right in the ballpark at 16 1/2 mpg. Here's what the gov't says the truck gets.

http://www.fueleconomy.gov/feg/noframes/6085.shtml

I've been reading about a product called Ethanol Defense. It's claimed to improve performance and economy. Check this out.

http://www.bellperformance.com/testi...f-2757c4742ce8