Go ahead and don't believe the numbers. The whole point of this article is to show how little tips and tricks can get you unbelievable fuel-economy figures-and it worked. If we hadn't been there filling the tank ourselves, we would've had a hard time believing the 30.94-mpg figure our cell phone calculator spit out after we filled the tank. There it was, though, we almost reached 31 mpg in a 1-ton dualie diesel all for the price of $9.26 in modifications.
It all started when we talked about different ways to increase our '97 Dodge Ram's fuel economy. Getting 21 highway mpg in stock form (3.54 axle gears and an automatic) wasn't bad, but there was more to be had. Reducing rolling resistance, improving engine efficiency and the truck's aerodynamics, and becoming more aware of your driving habits are all a big part of increasing fuel economy.
 To get the best fuel economy...  To get the best fuel economy possible, we needed less rolling resistance. The folks at American Tire couldn't take our dualies off for liability reasons, but they were nice enough to air our tires up to 70 psi. |  Less weight also equals more...  Less weight also equals more mpg. Without a trailer to tow, our fifth-wheel hitch was just a big anchor, so we took it off and saved about 75 pounds. |  How you drive can make a huge...  How you drive can make a huge difference in fuel economy. If you're stuck in traffic like this, don't expect to get great mileage. |
Rolling Resistance
This one was pretty easy. The point was to use low- or no-buck modifications, and only so much could be done to reduce the friction between the tires and the road. The recommended tire pressures for our vehicle were 65-psi front and 60-psi rear. Our actual pressures when measured turned out to be about 55-60 psi all around, so we had our tires inflated to 70-psi front and 65-psi rear to get a little less rolling resistance and a little more mpg.
 Any improvement in aerodynamics...  Any improvement in aerodynamics is worth some power, so we whipped up these neat cardboard discs to cover the lugs on our wheels. |  The mirrors were folded in...  The mirrors were folded in and the windows were kept up for less aerodynamic drag. Believe us, stuff like this works. |  It's amazing what duct tape...  It's amazing what duct tape can do. Even after 100 miles of 60-mph speeds, it held firm on the wheel. |
Engine Efficiency
This one was a little hard without any type of tuning available because our 12-valve Cummins is mechanical, and we couldn't put in an economy tune anywhere. We heard diesels liked running a little hot, so the electric fans on the truck were turned off until engine temps reached 210 degrees F. Other than that, no changes were made to the engine.
Aerodynamics
This is where things got fun. Ultrahigh mpg hybrids have incredible aerodynamics. The Toyota Prius, for instance, has a drag coefficent of 0.26 compared with a Z06 Corvette's 0.36 (a truck comes in at 0.40-0.45), so aerodynamics play a large role in mpg. They don't call it 200-mph tape for no reason, so with a $9.26 roll of clear duct tape, we were in business. We taped off everything we could, made special aero hubcaps out of cardboard, and even blocked the grille off for aerodynamic purposes-even though many people we talked to were sure the engine would overheat. We drove with the windows up and the mirrors folded in to get every last bit of aero we could out of our truck.