How To Improve Fuel Mileage With Three Simple Mods

It’s no secret that diesel is expensive these days. In fact, it’s something we’re painfully aware of (or see complained about) on a daily basis. Never fear though, there are a few things you can do to reduce those visits to the pump and improve fuel mileage, no matter what kind of diesel-powered ride you own. Diesel engines are very efficient, but there’s always room for improvement, whether it be with the help of tuning, the type of oils used, or simply your driving habits.

In this article, we’ll be looking at three big factors to help improve fuel mileage. The first will involve the fuel itself. How many here have ever tried a fuel additive or Cetane booster like Hot Shot’s Secret Every Day Treatment additive? For the second improvement, we will look at tuning and increased efficiency through the use of a hand-held tuner.  For this article, we’ll check out Bully Dog‘s GT Tuner. Finally, we’ll take a look at oil, the “lifeblood” of an engine, to see where improvements can be made with the help of AMSOIL.

Hot Shots secret

Hot Shot Secret’s Everyday Diesel Treatment is a great way to increase mileage.

Adding To Your Fuel To Improve Fuel Mileage

If you’re looking for an “easy button” type of modification that requires almost no effort yet results in better fuel economy, then one of the first steps involves not your engine, but your fuel. The diesel that we get here in the USA is considered some of the worst diesel fuel on the planet, with low lubricity (what keeps your injection system in good shape) and a very low Cetane rating (think of it as octane, but for diesels). The result of this is a low-energy fuel that doesn’t lubricate your engine very well. Sounds bad right? Well, it’s not good.

There’s nothing that says diesel fuel can’t be improved, and a fuel additive such as Hot Shot Secret’s EDT does just that. In fact, we have been using it in our daily driver (Project WorkHorse) for the last couple of years. We’re not scientists, but we are told it increases lubricity by 26 percent and raises Cetane levels by seven points. This results in a more efficient-burning fuel. Independent tests (as in, not done by Hot Shots) concluded that an average mileage gain of about 7.3 percent was the result of adding EDT to a tank of fuel and running down the road. Now of course since mileage varies, so will the actual “MPG gain,” but in our daily, we saw a 1-1/2 to 2 mpg improvement.

One of the comments we often hear is, “those additives make the cost more than the mileage gains?” As of this writing, diesel is $6.00 a gallon, so we’re going to say no! A 16-ounce bottle is enough to treat 400 gallons of diesel fuel with a premium dose, or 200 gallons with a performance dose. Even at the 200-gallon level at current prices, that’s just an additional $3.50 per tank of fuel. However, it can result in a savings of 1.7 gallons, or $10 per 35-gallon tank. So, in these times, can you afford NOT to hot rod your diesel fuel?

Bully Dog GT

A hand-held tuner is a great way to improve how your diesel runs.

A Simple Tune Can Improve Fuel Mileage

Another area where there’s a significant improvement to be had is through computer tuning. Diesel engines still rely on things like air/fuel ratios and injection timing to create power efficiently. And even though the factory tuning is very good, there’s almost always a little wiggle room for improvement. One company that has been doing it as long as heavy-duty pickups have been computer-controlled is Bully Dog.

Although Bully Dog has a full line of gas and diesel tuners, probably its most popular product is its Gauge Tuner (GT). The Bully Dog GT for diesels is a tuner that offers power increases and can improve fuel mileage for virtually all modern electronically-controlled diesel pickup trucks. The Bully Dog GT has multiple settings for everything from street to towing to race, has adjustable speed and Exhaust Gas Temperature (EGT) limiters (EGT is used as a safeguard), and can even read trouble codes. This is one of those modifications that can increase mileage (usually 1 to 3 mpg depending on driving) but there are a ton of other benefits too.

improve fuel mileage

We had the chance to recently test a GT on both a ’05 Chevy Silverado 2500HD with a 6.6L Duramax and a 2019 Ram Cummins. The power results noted with the Duramax were impressive. The truck went from 248 rwhp to 363 rwhp (on the max setting). The owner reported a nearly two mpg increase under normal driving, and around one mpg when towing. That’s quite a difference. As far as our Ram, we tested it on a long trip with a loaded gooseneck trailer and you can see those results here. If you’re super economy-minded, you can also use the EGT gauge to achieve your best economy (you will need to purchase and install the probe separately). The Bully Dog is also compatible with all modern emissions equipment and can help with improved shifting, de-fueling, and regeneration.

All Lubed Up

When rolling down the highway under normal conditions, your diesel pickup doesn’t take much horsepower to keep rolling — some claim as little as 20 to 30 horsepower. To this end, when you’re looking at fuel economy, it’s true that any little horsepower gain under light engine load and low-RPM matters, such as gains that can be provided by engine, transmission, and axle oils.

When a large load is put behind a diesel and it’s tasked to use a substantial amount of horsepower, the mileage can drop considerably. Oil can have a dramatic effect on the engine here. Everything in the engine will be hot and under an extreme load, so having a slick, lubricated bearing surface is of the utmost importance for maximum reliability.

improve fuel mileage

When you use your diesel to haul things, getting the best fuel mileage possible is a huge concern.

AMSOIL claims that when using their oils, wear protection is up to six times better than with conventional oils. This means less friction and improved fuel mileage. AMSOIL also offers double the rust protection, and fights against harmful deposits, leading to 60-percent better turbo cleanliness. For an all-out economy effort, AMSOIL makes transmission fluid and gear oil too. Initially, it might be more expensive, but the improvement in wear and longer intervals between oil changes can definitely offset the cost.

improve fuel mileage

If your throttle foot tends to get heavy, the Bully Dog tuner has an efficiency coach built in to help you see exactly how your heavy foot affects mileage.

Class 8 Semis, Fleets, And Economy Cars

While we’ve mostly referenced diesel pickups in this article, the products highlighted will work on any diesel-powered vehicle, from a VW Jetta to a Freightliner semi-truck. When you’re looking at vehicles that get really bad (or really good) mileage or often travel long distances, these modifications can be even more effective. Diesel BMWs for instance, are known to really excel in the mileage department when tuned, and gains of 5 to 8 mpg aren’t uncommon. If you’re playing the percentage game, even small gains (like the 6.54-percent gain in AMSOIL’s class 8 test) can and will add up when you’re talking about potentially multiple trucks operating over tens of thousands of miles a year.

Going Easy On The Pedal Will Improve Fuel Mileage

While it’s true that all of these subjects mentioned can help improve fuel mileage, it goes without saying, you still need to be mindful of how you drive. Even slowing down five miles per hour (if you’re a speeder) can save a few miles per gallon. Your average best efficiency for fuel economy in a diesel truck is around 1,500 to 1,800 rpm, so try to keep it there (unless you need more RPM for towing). Are your tires old and cracked? You might want to look into that too and up the pressure a little bit. Maximum tire pressure on an E Load Range tire should be reserved for towing, but running them at around 60 psi is a good balance between ride and fuel economy.

Slamming on your brakes and then accelerating hard is another fuel-sucker, and while we’re not expecting you to coast everywhere, maybe try and keep your hot-rodding to a minimum. Aerodynamics matter too. Low front air dams, camper shells, and tonneau covers all help too. Finally, those 22- or 24-inch wheels and giant tires might look cool, but also keep in mind they’ll tank your mileage.

Building a Better Vehicle

One thing that we should point out is that virtually every fuel-saving product mentioned also creates a better all-around vehicle. A fuel additive will keep your injection system lubed, alive longer, and lead to better reliability. A tune will offer more power and mileage as well as features like data monitoring. A quality synthetic oil will offer superior engine wear prevention and longer life. Although everything mentioned will help you combat the high cost of diesel, it will also help in a number of other ways too. With everything combined, we’d expect to see you improve fuel mileage by four to six miles per gallon on your average diesel pickup, which is quite a bit when you add it all up! So don’t let high fuel prices get you down, make a change, and start saving money now.

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About the author

Jason Sands

Jason Sands has owned everything from an 8-second Nova to rat rods. His claim to fame is setting the Guinness World Record for the fastest speed towing a trailer at 141.998 mph in a diesel-powered GMC Duramax. He's also known to write on occasion.
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