Can You Improve Fuel Mileage With A Bully Dog Tuner? We Test It

The price of fuel right now is high enough to make everyone cringe when pulling into the pump and then look for ways to improve fuel mileage. As of this writing, diesel is $5.65 a gallon where I live in central Florida. While that is not as bad as some places, I have a trip to Pennsylvania planned, and as I go north, apparently, so does the price of diesel.

I do what I can to make my truck as fuel-efficient as possible, but the northbound trip will also include a loaded gooseneck trailer (nearly 10,000 pounds). Diesel consumption is a concern and I wondered if there was anything — other than the obvious soft application of the right foot to the pedal — that I could do to curb my RAM’s fuel consumption.

The Bully Dog tuner comes with everything you need - for most trucks. For 2018 and newer RAM trucks, you need to also get a bypass wire kit. The RAM-specific connector (right) is denoted by a red stripe and the bypass wire is a small connector that gets plugged in under the dash.

I realize there are a few things I can do to reduce fuel consumption: again, go easy on the throttle, proper maintenance, and properly inflated tires. But is there anything else that will increase the miles I travel per gallon of fuel my truck uses? What about installing a hand-held programmer? I have heard many enthusiasts say they have gotten good results by adding one, so I thought it might be a good investment. After some research, I decided to give one a try and found Bully Dog actually has two that work with my 2019 RAM.

Decisions, Decisions…

Since I needed to decide which one to use, I reached out to Bully Dog and spoke to Jill Hepp, marketing director at SCT/Bully Dog to learn the differences. “It comes down to preference,” she states. “The Gauge Tuner (GT) is the best option if you want to monitor the vehicle and keep [the device] on the dashboard. I would choose the BDX if you are looking to get custom tunes in the future. There are a lot of features with both, but for a simple stand-out item, that would be my suggestion.”

The RAM-specific required bypass wire connects to a terminal block under the dash on the driver's side kick panel area. The red arrow shows the wire in the proper location. The other end connects to the Bully Dog OBD-II connector.

Another aspect that might help you decide between the GT and the BDX is the BDX is Wi-Fi-enabled while the GT is not. That means the GT does need a computer connection for updates and to upload any data recorded but you can update the BDX from almost anywhere.

To keep things simple, I decided to utilize the GT. Before I go any farther, I know you all realize the importance of maintaining emissions-legal parts on your trucks, right? I plan to do so and avoid any problems down the road. As far as unsanctioned mods, Bully Dog is adamant they be avoided. In fact, no SCT/Bully Dog tuning devices will modify or delete vehicle emissions and the products comply with the Clean Air Act. According to Bully Dog, “tunes that are preloaded in our devices have gone through hours of testing to ensure the safety of the drivers and the environment overall. Custom tuners are required to follow the guidelines of the Clean Air Act as they develop their own tunes for our devices.” Okay, the legal stuff is out of the way.

I Have A Plan

To complete my test, I was planning to drive to Muncy, Pennsylvania while hauling my loaded 26-foot gooseneck. The weight was just shy of 10,000 pounds. On the way north, I would rely on the factory RAM tune. Before I was to start the return trip, I would upload the “Towing” tune in the GT and then return to Florida. Seemed like a plausible idea and I hoped it would improve fuel mileage.

In case you are wondering, the route I chose started out on 98 North in Lakeland, Florida. Outside of town, I jumped on 471 North until I got to 301. I took 301 to I-10 East to 295 around Jacksonville, Florida. After I exited 295 onto 95 North, I  went straight through several states. Roughly halfway through Virginia, I turned left onto Route 66 West to 81 North until I hit 11/15 North. In Selinsgrove, Pennsylvania I took 220 North to Muncy, Pennsylvania (my destination). The return trip used the same route. Full disclosure: the return trip did include my wife and more stuff that she apparently thinks we need in Florida, so the load was a little heavier traveling back home. Finally, I kept the cruise control set at 68 miles per hour whenever possible.

By the way, all mileage was calculated by actual math, not by the usually not-so-accurate digital readout on the dash. The trip logged 1,121 miles each way. The trip north netted 11.2 mpg. I also need to mention that the truck tires were set at 60 psi and the trailer tires at 80 psi.

Once the program is downloaded from your home computer or laptop, the device can be connected to the truck and the tune uploaded. The Bully Dog GT can display many parameters, and you choose which ones you want to monitor.

The Voodoo It Do To Improve Fuel Mileage

But what does the GT tuner actually do, and would it improve fuel mileage while traveling back to Florida? What the GT offers are three pre-configured tunes (Towing, Performance, and Extreme) and all three are designed to deliver a desired degree of performance enhancement. Personally, I was interested in Towing mode.

If you want to monitor your vehicle’s engine parameters, The GT allows you to view the vehicle’s PCM data on the device or a PC. But here’s the claim that everyone cares about. It increases your vehicle’s horsepower, torque, and throttle response, and it can even improve fuel mileage. Finally, it also reads and clears PCM diagnostic trouble codes.

improve fuel mileage

One aspect of the GT device is the Efficiency Coach. This little window will let you know how efficiently you are — or are not — using the throttle pedal. I was actually impressed that my driving habits before and after the GT install were very similar.

I quickly learned that uploading the program to the GT is fairly easy, as Bully Dog supplies an SD card and card reader for you to download the appropriate vehicle parameters. Yes, the GT is a universal tuner designed to fit many vehicles. You will need to download the correct vehicle tune. To do this, you slide the SD card and reader into any computer with a USB hub, connect to the Bully Dog website and follow the instructions for downloading.

Updating can also be done by inserting the SD card into the GT device and plugging that into your computer, or with a Wi-Fi connection. Once that’s done, put the card in the device and you’re ready to plug it into your vehicle. If you’re like me and have a newer RAM, you do have some extra wiring to connect under the dash, but that is even plug-and-play.

If you are connecting to a 2018 or newer RAM truck, this extra wiring is an additional “bypass cable” that needs to be connected. What this cable does, is, heck, I don’t really know, so I asked Jill for some clarification. “I spoke with the engineering team about the cable to see what I can share, and they are concerned about giving too much detail as that is part of our secret sauce of tuning,” she says with a sly grin on her face. “However, they did tell me this, ‘the Cummins bypass cable establishes the most efficient communication connection between our device and the vehicle.’” Okay, I get it, she could tell me, but …

Putting The Plan Into Action

Again, my current interest was solely about towing, so after I uploaded the tune into the RAM, I made my tuning selection as such. I am by no means an I.T. wizard. My interaction with computer programming is limited, so I was a little apprehensive about uploading the program to my truck’s computer. What happens if I mess it up? Will I erase the OE program on the truck? I learned that if you follow the prompts on the device’s screen, you have nothing to fear.

Anyway, with the Bully Dog “Towing” tune uploaded, I was ready to make the journey south. I once again made sure the truck and trailer’s tire pressures were where they should be (truck 60 psi and trailer 80 psi), I pulled out of the hotel at 6:30 a.m. on Sunday morning and when I made it back home to Florida it was Monday morning at 5:30 a.m.

improve fuel mileage

The test subject was a 2019 RAM with a Cummins. The trailer is a 24-foot Maxx-D Trailer that was loaded with a 1967 Plymouth Valiant and a full-dress Harley Davidson motorcycle. Altogether, the trailer weighed 9,790 pounds going north, and the trip back south was 250 pounds heavier.

Before I started this test, I was skeptical about whether a tuner could help improve fuel mileage. I wondered if this $460.00 device would be worth any improvement. When I did the math for the return trip, I learned the RAM had delivered 13.3 mpg. That equated to a 2.1 mpg and 18.75-percent increase. That is substantial in my book.

Now that the test is over and the Towing program proved it is worth its weight in diesel, I now need to play with the Performance and Extreme modes and see what kind of gains they deliver. I know I can’t tow the trailer or haul much while in Performance mode, but there is no reason this workhorse can’t have a little fun and stretch her legs now and again.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.
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