Compare gas mileage estimates for 2008 pickups before you shop for a used truck. Estimates help you compare trucks within a class, but remember that you may or may not achieve the same results, since trucks (or cars or suvs) are not fuel tested in real-world conditions.
Chevy gave the Colorado a power boost in 2008 by adding two new engines. Fuel economy ratings went down somewhat, but the decline had more to do with the new testing system than it did the new engine choices.
Silverado and Sierra half ton trucks share a good percentage of features, so you'd expect that fuel mileage estimates are about the same. They are, with just a few exceptions.
All Dodge Ram 1500 trucks run on regular gas and some are E85 compatible. The lowest mileage estimate for 2008 is 9-mpg city and 12-mpg highway for trucks running on E85. The highest is 16/19 for the 2WD 6-cylinder Rams. Other Ram ratings fall between those numbers.
It isn't surprising that performance-oriented versions of the F-150 are rated to get significantly lower miles per gallon than trucks in Ford's remaining lineup. You'll find 2WD trucks at the top -- six cylinder and eight -- and a dip when you crossover to the 4WDs.
The Ford Ranger truck tops the EPA's light truck fuel economy ratings list (along with its relative, the Mazda B2300). The higher mileage Ranger might not have all of the other features you're looking for, but if fuel savings is your goal, it's worth a look.
GMC's Canyon is a whole lot like a Colorado with a different skin. Expect to see similar EPA fuel economy ratings for both trucks.
With gas where it is, it's difficult to look at all those teen ratings in full-size truck fuel economy estimates. The Sierra isn't alone -- but let's hope the 2009 hybrid's gas usage projections take a healthy jump upwards.
You can buy a basic 4-cylinder 2WD Tacoma truck that gets pretty good gas mileage. Go for either more options or a 4WD truck and you'll find that the mileage estimates drop dramatically -- something that's not unusual for any vehicle.
Toyota's newest generation Tundra is a workhorse, but its fuel economy ratings are slightly lower than comparable pickups.