In terms of fuel consumption, all major OE manufacturers leave room for improvement. It is no secret that the internal-combustion engine falls short when converting a gallon of fuel into motion. Typically, fuel efficiency on modern gas engines falls somewhere between the 60 and 80 percent range. This means that 20 to 40 percent of the fuel you pump into your tank is lost as heat, noise, and/or emissions. Diesel engines offer a slightly better return on a gallon, but as so many who already own a diesel know, the rich oil tycoons have agreed to punish those of us with a preference for oil-burners, charging upwards of $4.50 for a single gallon! Is it fair? Heck no. Can you do something about it? Heck yeah. Check out the fuel-saving products we tested on an '03 Dodge Ram 3/4-ton turbodiesel. The results were outstanding, netting significant improvements in mpg. While this article features diesel tech, there are plenty of applicable mile-saving tips in this story for those of your who run conventional dino-juice, too.
Our test truck belonged to Kilby Enterprises. It was picked because its owner, Brad Kilby, didn't mind us racking up some 17,050 miles over six months to generate data on our test products. We also picked the truck because it represented what we think a majority of our readers might own, especially those who are concerned about fuel economy. Equipped with four-wheel drive and an automatic transmission, this quad cab longbed started our test with 44,329 miles on the clock. Kilby had already installed a 4-inch after-cat exhaust system, a cold-air intake from aFe, and a leveling kit to clear 35-inch mud tires. The rig hadn't ever seen the stellar mpg numbers in this arrangement-at least, not the numbers you would expect from a Cummins diesel, but Kilby didn't drive the rig on the highway very much to start with. The first thing we needed to do was generate some baseline data. To do this we drove the truck all over California loaded and unloaded for 2,020 miles. During this phase of the test, the truck returned an average fuel economy of 13.56 mpg. These test miles consisted mostly of highway cruising, 55 to 70 mph, nearly a quarter of which was spent towing (527 miles) our Project Teal Brute on our Carson flatbed trailer, a total combined weight of 18,490 pounds. We wanted to generate data the same way most people would use this type of truck. As such, towing was a necessary portion of the test.
To keep things fair, we used No. 2 diesel fuel purchased exclusively from Chevron gas stations. We kept track of mileage, gallons pumped, and each station's price per gallon to demonstrate just how much diesel prices fluctuate here in the western region of the country. The most expensive price we paid was $4.99 per gallon, while the best price was $4.11. In the end, our average price paid per gallon was $4.42. Averaged out over 48 fill-ups, this equated to 355.20 miles per fill-up.
One item we hear a lot of folks debating about these days is programmers. Many options exist in this area of the aftermarket that claim to increase fuel economy while adding power at the same time. We wanted to test this claim for ourselves to see just what kind of improvements could be untapped with an electronic gizmo. After much research online about different programmers, we decided to test the Smarty by MADS Electronics. The Smarty S-06 is super-easy to use, requiring just under five minutes start to finish. The unit allows end users to select from 10 different performance settings. Each setting changes a variety of engine parameters including timing, fuel pressure, and boost fooling. The Smarty also allows users to adjust the top speed limiter, recalibrate the ECU for different tire size, and allows users to diagnose trouble codes via the OBD-II port. We set the Smarty to setting No. 2 as recommended for fuel savings by the included product manual. This setting suggests gains of up to 2 mpg, though we did not see this. What we did find after setting the Smarty to level 2 was quicker throttle response and faster turbo spoolup. Fuel economy remained consistent during our testing, though a noticeable "snappiness" made the truck a lot more fun to drive. The Smarty product line is available through KLM Performance, an online resource for suspension, drivetrain, and engine performance products.
One important detail to note about the way we did our testing is fill technique. We wanted to get consistent results from each fill-up. So early on, we established a procedure to prevent anomalies. This consisted of filling the tank until the pump shuts off automatically, waiting 10 seconds and then continuing dispensing fuel until the pump shut off once again. We knew if we topped off any one tank, our data could be compromised. The truck's fuel tank held approximately 34.5 gallons of diesel.
The next thing we tested was the air filter. In most cases a dirty air filter will affect fuel mileage on a gasoline engine. In this case, due to the fact that the truck was a turbodiesel and Kilby hadn't cleaned his aFe conical filter element for quite some time, we didn't know what to expect. As seen here, a thick layer of dusty grime coated the filter's entire surface. Once clean, we ran a tank of fuel through the truck at highway speeds and noticed no substantial change in fuel economy. We suspect that the lack of noticeable increase had to do with the fact that the turbo pulls a great deal of air volume through the element regardless of restriction. This is one of the nice things about running a filter element with increased surface area.
Dynatrac is a known leader in drivetrain components worldwide. The Free-Spin manual hub conversion is a product that is said to offer improvements in fuel economy to the tune of 2 to 3 mpg. The way it works is simple: By eliminating the rotational resistance or drag of front axle and differential parts, you eliminate friction. As we all know, friction robs horsepower and in turn, fuel economy. We like the fact that the Free-Spin setup prolongs the life of all front axle parts significantly by simply letting them sit stationary instead of spinning as the truck moves.
With our baseline data recorded, we started our product testing with a new set of Nitto Dune Grappler tires and a front-end alignment. We figured this would enable us to generate results with greater accuracy over the old, worn-out Pro Comp XTerrains Kilby was running prior to our modifications. Another reason we did this was to see if an alignment, or a less aggressive tread, would actually affect fuel economy. Once completed, we didn't notice any significant changes in mpg, though these additions gave us greater confidence collecting further test data. All testing was performed with tires inflated to 45 psi at each corner.