1997 Dodge Ram 3500 Dualie Cummins - Diesel Power Magazine

Driving Habits
Changing driving habits proved to be a big factor. We slowed down to 60 mph wherever we went, coasted down hills whenever possible, and put a block under the gas pedal to limit us to half throttle while climbing hills. Under full throttle, our gas mileage would sink to about 10 mpg, so we had a throttle block to keep us from flooring it when we got antsy.

The grille is just a thin mesh, so under normal circumstances, your engine compartment is acting as a large parachute under speed. To combat this, we had the entire front of the grille blocked off with cardboard, leaving only the foglight holes (arrows) for air to pass through and cool the vehicle. Oddly enough, this seemed to be enough to keep things cool-even going up hills.
The grille is just a thin mesh, so under normal circumstances, your engine compartment is
It sure looks aerodynamic. Who would've thought it would actually work? Even if each modification only minimally affects mileage, it all adds up.
It sure looks aerodynamic. Who would've thought it would actually work? Even if each modif
There is no doubt the truck ran hot with the grille blocked off. Normally, the truck reaches 190 degrees, the thermostat opens, and the truck cools to 160 degrees. The whole way across the desert, it stayed at a steady 200-210 degrees (we were ready to pull over if it hit 220), even when we later floored it up a few hills to see if it would overheat. Don't try this with a trailer.
There is no doubt the truck ran hot with the grille blocked off. Normally, the truck reach

The Results
How did it all come together? Imagine driving a truck that's running hot with the windows up at 60 mph across the desert, the mirrors folded in so you can't see, and no A/C because it creates more engine drag. It was hot and miserable inside the cab, and at 60 mph, we didn't pass a single car.

Breathing through just the foglight holes, the truck never even got close to overheating. The engine temperature stabilized at 205 degrees without the fans even coming on. The result of all these shenanigans was a ridiculous 31 mpg.

To keep us from getting throttle happy, a throttle stop was put in; we used a connecting rod we had around the office. The throttle stop only let us get to half throttle, which helped us save valuable mpg.
To keep us from getting throttle happy, a throttle stop was put in; we used a connecting r

In follow-up testing (to see if the figure was a fluke), the truck still averaged 26 mpg at speeds ranging from 70-80 mph with just the tires aired up and the grille blocked off, making our 31-mpg number seem believable. We also measured this as purely highway mpg, from freeway-exit gas station to freeway-exit gas station to make sure we had a fair comparison between modifications-no city traffic at all.

The funny part is we think we could still get more out of it. We didn't seal the bed off with any kind of cover, we didn't take the rear dualies off for less weight and less rolling resistance, and we didn't lower the truck. Although this article was done mostly for fun, there is no reason a properly lowered rig with low-rolling-resistance tires and a gear change shouldn't get 25 mpg on the highway.