The price of Diesel fuel has finally come down some, but not nearly back to pre-Katrina levels. It appears that $2.50 plus per gallon prices are here to stay. This frequently brings up the question of what can be done to save fuel and how much do these performance products help with the fuel efficiency of light duty diesel pickup trucks.

I won't bother to go through the typical litany of efficiency items, tire pressure, clean air filter, etc, as you can get that anywhere. Since we at Grimm Performance sell a lot of Quadzilla products, we are going to discuss how to select or use the ones that you have for the best results. Most of the information will hold true whether you drive a Dodge Cummins, a Ford Powerstroke, or a Chevy Duramax.

After spending some time with the guys at Quadzilla and doing a LOT of our own experimenting, we have come to some conclusions. For around the town driving, or for towing, the 60-70HP range remains the best for improving overall fuel economy, BUT, that is not necessarily true for the open highway.

We took four trucks and had the owners check the mileage with the odometer and gas pump instead of the trip computer. We used an 01 Ford 7.3L Powerstroke with the Quadzilla 100HP module, an 05 Ford 6.0L Powerstroke with the Quadzilla 160HP module, an 03 Dodge Cummins with the Quadzilla 140HP module and an 05 Dodge Cummins with the Quadzilla 100HP module. Driving conditions ranged from 11,000 feet in the Rockies to sea level in Miami.

In all cases, the worst fuel economy improvements that were seen were just under 2mpg with some very heavy loads. The average was between 3 and 4 mpg. The surprising thing, and the point of this article, was that for unloaded highway driving, the 100 to 110HP range yielded 1 to 2 MPG better fuel economy than did the 60 to 70HP settings.

My personal theory is that the wind resistance of one of these trucks above 70mph bleeds off a tremendous amount of horsepower, resulting in more pedal for the same speed. The higher horsepower settings allow less throttle to be used to achieve highway speeds. This was found to be very true on a run between Denver, CO and Phoenix, AZ where speeds were reported around 90mph for sustained periods in the 05 Ford 6.0L. The name of this driver will certainly not be mentioned!

There is a point of diminishing returns, as the race settings start pushing the economy back to areas close to stock. If you want to make the big horsepower, it does require some extra fuel!

So, here are our recommendations. If you don't want to put up a lot of money, go ahead and get the Quadzilla XZT line for the Ford Powerstroke or Dodge Cummins. This product is set at the best all around point for towing, city, and highway driving. If you are willing to part with a little more cash, get the Quadzilla Standard box, 110HP for the Ford 6.0 or 100HP for the Dodge Cummins, and make those adjustments for your driving conditions. Both Quadzilla programmers available for the Duramax have the kind of settings that you need as well.

For you speed freaks, have no fear, Quad included those middle settings on your boxes too! You can tell everybody that you bought the box to save fuel and still smoke your buddies on the track!