We sold our 2003 Chevrolet pickup in February and bought a 2007 extended cab with a smaller (4.3 liter V-6) to save a little on fuel and also to give us more room in the cab so we could take friends and/or our two Golden Retrievers.  Our 2007 pickup gets better mileage than the 2003 with the 4.7 liter V-8 on the highway without the trailer, but uses a little more fuel when towing the trailer.  However, since most of the miles are without the trailer we are happy.

We did find the V-6 a little underpowered while towing the Casita on some of the very steep mountain roads and at altitudes about 9,000 feet, but we just used a lower gear and had no problems.  We have a 4-speed automatic transmission in the pickup with a 3.23 ratio differential.  We also have a transmission cooler which helps keep the transmission from overheating.

With the trailer the pickup averages from about 11 to 14 mpg depending on a variety of variables including winds, altitude, type of road, and speed.  Without the trailer the pickup has been averaging from about 16 to 21 mpg depending on some of the same variables.