This is probably the number one question we get every day. Even more so with the new trucks coming out. They have enough power to meet the owner’s needs, but the high price of diesel fuel makes fuel economy top of everyone’s mind. The following tips apply to all diesel trucks, including Ford Powerstrokes, Dodge Cummins, and Chevy/GMC Duramax. These are very basic steps that you can do for little or no money and can help you earn some miles per gallon. There are plenty of other expensive things like programmers that will dramatically increase horsepower, but we’re just looking at relatively inexpensive things the average guy can do to get his mileage up a bit without spending a ton of extra money.
1. Maintenance:
You’d think this might be a no-brainer, but you’d be surprised by the number of trucks that come through our shop that perform completely different after we’ve given you a full service. If you want to get the most efficiency out of your diesel truck, you need to make sure that all of the vehicle’s systems are working properly. I cannot stress enough how important clean air and fuel filters are to the proper operation of your truck. If any of those filters are not at full capacity, their potency will suffer. You will have to run the truck much harder to do the same job. A clogged air filter can steal 15 to 50 horsepower. Similarly, oil that is long overdue for change loses its lubricity and causes additional drag. It’s just not doing as good a job as fresh new oil. This extra resistance steals power. This also applies to transmission, transfer case and differential oils. If your gears have to turn through thick, rotting mud, it will rob you of some power, which in turn reduces the efficiency of the truck as a whole. In short, establish a maintenance schedule that includes all fluids, filters, and service items. If your truck has over 75,000 miles and you’ve never changed the transmission or diff oils, it may be a good time to do some extra maintenance.
2. Synthetic lubricants:
Ok, to be honest, I’ve always been skeptical of a lot of the claims that come next to bottles of synthetic lube. I’ve probably had at least two hundred Amsoil salesmen telling me how good the oil is and if I just changed all the oil in the truck I could pick up two or three miles to the gallon. Now, I can’t beat either Amsoil or Royal Purple. I have used both for years in many of my performance vehicles and they provide excellent protection. I have no doubts about its superior lubricating ability in demanding conditions. But what about these mileage claims? Well, believe it or not, they are true! We have had many customers over the years bring their truck in for a complete change. We changed all truck oil to synthetic oils, including: engine oil, transmission oil, transfer case oil, and front and rear differentials. I was finally sold on the increase in mileage when we switched to some of our clients who run fast trucking companies. These guys rack up crazy miles every month and they wanted to switch to synthetic so they could extend the life of the oil along with the extra protection for hard working trucks. They are also meticulous about tracking mileage. On average, they all picked up two miles per gallon after switching to synthetic. Synthetic oils just do a better job of lubricating the truck’s moving parts, so they provide less drag. Every time we can free up some horsepower to move the load, the fuel economy will increase.
3. Check your momentum:
This could probably be included in the maintenance topic, but it’s so important that it deserves its own discussion area. Many people seem to be uninterested in the boost level of their engine. I hear all the time, “I don’t need a boost gauge. It’s useless, it’s fun to watch.” While that may be true most of the time, the real purpose of a boost gauge isn’t just to see how much boost you’re generating in a performance application. Boost is very important to the performance of a turbocharged diesel. It varies from truck to truck, but boost is in direct relation to the amount of power your truck generates. Simply put: more boost = more power. So why have a momentum gauge? If you know that your truck by its power level is supposed to have 20 psi of boost, you can spot small problems that go unnoticed by most. These little problems are removing boost somewhere in the system and reducing the power output of your engine. The average driver won’t notice a difference in the seat of their pants between 18 psi and 20 psi.
A lot of people will keep driving wondering why they don’t get as much power and mileage as they used to. If they had a momentum indicator, they’d have a clue where to start looking. Maybe there is a loose clamp or a broken intercooler boot. Maybe a small leak in the exhaust pipe that drives the turbo. Or maybe the air filter or fuel filter is starting to get dirty. A loss in boost pressure is always a sign of a problem somewhere in the engine. If you’re always keeping an eye on it, you can catch these little problems long before you normally and consistently have a great truck running. It’s not unusual for a truck to come into the shop complaining of low power or poor fuel economy only to find that it’s only making half the boost it should. Further probing may find a dirty air filter, faulty turbo, or a host of other issues. The sad part is that the customer has driven the truck like this for a couple of months because he really had no idea he had a problem. It just didn’t seem to work as well as it used to and problems usually get so bad gradually that they don’t think to start looking for trouble. If they had a momentum gauge, they would have known about it long before it got to us.
4. Keep your RPMs low:
As diesel trucks become more popular and more widely used, more people than ever are switching from gasoline engines. The big problem is that they still drive them like a gasoline engine. And if you want to drive that way, you won’t hurt the engine at all, but your fuel economy will suffer. For the best fuel economy, diesels generally like to laze around while doing their job. While newer trucks make impressive power at higher rpm, low-end torque is where it’s at for maximum fuel economy. If you’re trying to scratch that last mile per gallon, be careful with the gas pedal. Use only the minimum amount of acceleration to get to the desired speed. The sooner you can put your truck in overdrive and let the torque move the load down the road, the better fuel economy you’ll get. We have a customer who has a really nice 7.3 Powerstroke that we take care of. He drives the truck very easily and to be honest one would think the gas pedal is made of glass and he is afraid of breaking it if he pushes it too hard. You consistently get 25-26 mpg with that truck. If your son takes it, he can’t get more than 18 mpg. Of course, his son drives it with a little more spirit than dad. 😉
5. Let it breathe:
So, in conclusion, if you followed the five steps outlined above, I wouldn’t be surprised to see an increase of two to five miles per gallon depending on the current condition of your truck. You may already be following these steps right now. If you are, good for you. You are in the minority of diesel owners. If you’re not, there’s no time like today to get started!
To improve the efficiency of the engine, we need to get more air in and more air out. To increase fuel economy I suggest doing a little work on the fresh air intake side of the engine and also on the exhaust side. Now I know I said we weren’t going to try to spend a ton of money here trying to get better fuel economy and you’re probably wondering about this. I’d also like to let you know that we carry a complete line of performance exhaust and cold air intake kits for all diesel trucks from many different manufacturers. (Shameless, I know) But to be honest, if you’re looking to help out a completely stock truck, you may not need to go to all the expense to see some improvement. Don’t get me wrong, a 4″ free flowing exhaust and cold air intake is definitely the best way to go if you have the scratch, but a little DIY work can show you some benefit.
First of all, any diesel truck that has a catalytic converter will almost always see better performance by removing it. (check local emission laws first) There are many ways to do this. The cheapest thing would be to remove it and beat the material out of it. The second would be to cut it down and install a section of pipe the same size that you buy at a trucking store. Just getting that out of there will usually get you a mile per gallon or so and a better running truck. For extra credit, you can also remove the muffler. That will also help a bit if you don’t mind the noise. On the intake side, simply adding a K&N-style free-flow air filter will go a long way. These filters will flow more air, which will generally lower exhaust gas temperatures and increase horsepower. We’ve had customers report an increase of a mile per gallon just by making this swap. It makes sense from a money standpoint, since you can usually buy a reusable filter like the K&N or S&B for one and a half to two times the price of a regular air filter. The second time you would have to change the normal air filter, the performance one is paid for. You are saving money from then on.