5 Secrets to Increase the Fuel Economy and Mileage of a Diesel Pickup

This is probably the number one asked question we get every day. More so with the new trucks coming out. They have enough power to satisfy the owner’s needs, but the high price of diesel fuel is keep fuel economy front and center in everyone’s mind. The following tips apply to all diesel trucks including Ford Powerstrokes, Dodge Cummins, and the Chevy/GMC Duramax. They are very basic steps that you can do for little or no money that may help you gain a few miles per gallon. There are many other expensive things like programmers that will dramatically increase horsepower, but we are just looking at relatively inexpensive things the average guy can do to increase his mileage a little without spending a bunch of extra money.

1. Maintenance:

You would think this may be a no-brainer, but you would be surprised by the number of trucks that pass through our shop that run completely different after we give it a full service. If you want the most efficiency out of your diesel pickup, you need to make sure every vehicle system is working properly. I can not stress enough how important clean fuel and air filters are to the proper operation of your truck. If either of those filters are not up to full capacity, your horsepower will suffer. You will have to run the truck much harder to do the same work. A plugged up air filter can rob 15-50 horsepower. Likewise, oil that is way overdue for change loses it’s lubricity and causes extra drag. It simply isn’t doing as good of a job as fresh new oil will. This extra drag robs power. This is also true for transmission, transfer case, and differential oils. If your gears have to spin through thick, broke down sludge, it will rob a little horsepower which in turns lowers the efficiency of the truck as a whole. So in short, get on a maintenance schedule that includes all fluids, filters, and service items. If your truck has 75K+ miles on it and you haven’t ever changed the trans or dif oils, it may be a good time to do a little extra maintenance.

2. Synthetic Lubricants:

Ok, to be honest I have always be skeptical of many of the claims that come on the side of the synthetic lubricant bottles. I have probably had at least two hundred Amsoil salesmen telling me about how great the oil is and if I just swap out all the truck’s oil, I could pick up two or three miles per gallon. Now, I can’t knock 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 on their superior lubrication abilities 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 who will bring their truck in for a complete switch over. We changed every bit of oil in the truck to synthetic oils including: engine oil, trans oil, transfer case, and both front and rear differentials. I was finally convinced of the mileage increase when we switched over a few of our customers who run hot shot truck companies. These guys rack up crazy miles every month and wanted to switch to synthetic to be able to extend oil life along with the added protection for such hard working trucks. They also are meticulous about keeping track of mileage. On average, they all picked up two miles per gallon after switching to synthetic. The synthetic oils just do a better job of lubricating the moving parts of the truck therefore providing less drag. Any time we can free up a few horsepower to use to move the load, fuel economy will go up.

3. Check Your Boost:

This could probably go under the maintenance topic, but it is so important, it deserves it’s own area for discussion. A lot of people seem uninterested in the boost level of their engine. I hear all the time, “I don’t need a boost gauge. It serves no purpose, it’s just 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 are making in a performance application. Boost is very important to a turbocharged diesel’s performance. It varies from truck to truck, but boost is in direct relation to how much power your truck is making. Very simply put: more boost = more power. So, why have a boost gauge? If you know your truck for it’s power level is suppose to have 20 psi of boost, you can catch small problems that go unnoticed by most. These small problems are bleeding off boost somewhere in the system and lowering the power output of your engine. The average driver is not going to notice the difference in the seat of their pants between 18 psi and 20 psi.

So many folks will continue to drive around wondering why they aren’t getting as much power and mileage as they used to. If they had a boost gauge they would have a clue to where to start looking. Perhaps there is a loose clamp or torn intercooler boot. Maybe a slight leak in the exhaust piping that drives the turbo. Or perhaps the air filter or fuel filter is starting to get dirty. A loss in boost pressure always is a sign of a problem somewhere on the engine. If you are always keeping an eye on it, you can catch these little problems long before you would normally and consistently have a great running truck. It is not unusual for a truck to come into the shop with the complaint of low power or bad fuel economy and we find it is only making half of the boost it should. Further probing may find a dirty air filter, bad turbo, or a host of other problems. The sad part is the customer has driven the truck around like that for a couple of months because they didn’t really have an idea that they had a problem. It just didn’t seem to run as good as it used to and the problems usually get worse so gradually that they don’t think to start checking for problems. If they had a boost gauge they would have known long before it made it to us.

4. Keep Your RPM’s Down:

As diesel pickups become more popular and more used ones are out there, there are more people than ever switching over from gas engines. The big problem is they are still driving them like a gas engine. And if you want to drive that way, you will not hurt the engine at all, but your fuel economy will suffer. For best fuel economy, diesels in general just like to loaf while doing their work. While the newest trucks are making some impressive horsepower up in the higher rpms, low end torque is where it is at for ultimate fuel economy. If you are trying to scratch out every last mile per gallon, go easy on that throttle pedal. Use only the minimum amount of throttle to get to your desired speed. As quick as you can get your truck in overdrive and let the torque move the load down the road, the better the fuel economy you will get. We have a customer who has a really nice 7.3 Powerstroke that we take care of. He drives the truck very easy and to be honest, you would think the throttle pedal was made of glass and he was afraid of breaking it by pushing to hard. He constantly get 25-26 mpg with that truck. If his son takes it, he can get no better than 18 mpg. Of course his son drives it with a little more spirit than dad does. 😉

5. Let It Breathe:

So in conclusion, if you were to follow all five of these steps outlined above, I would not be surprised to see a two to five mile per gallon gain depending on the present condition of your truck. Perhaps you already are following these steps right now. If you are, good for you. You are in the minority of diesel owners. If you are not, there is not time like today to get started!

To improve the efficiency of the engine, we need to get more air in and more air back out. For a bump in fuel economy I suggest doing a little work on the fresh air intake side of the engine and the exhaust side as well. Now I know I said we were not going to try to spend a bunch of money here trying to get more fuel economy and you’re probably wondering about this one. I would also like to let you know that we carry a full line of performance exhausts and cold air intake kits for all diesel trucks from many different manufacturers. (shameless I know) But to be honest, if you are 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 may show you some benefit.

First and foremost, any diesel truck that has a catalytic converter will almost always see better performance from removing it. (check your local emission laws first) There are many ways to do this. The cheapest would be to remove it and beat the material out of it. The second would be to cut it out and install a section of the same size pipe you buy from a truck shop. Just getting that out of there will usually net you a mile per gallon or so and a better running truck. For extra credit, you could remove the muffler as well. That also will help a little if you don’t mind the noise. On the intake side, just adding a K&N style free flowing air filter will help out tremendously. These filters will flow more air which usually will lower your exhaust gas temperatures and increases horsepower. We have had customers report a one mile per gallon increase by just doing this swap. It makes sense money wise since you can usually buy a reusable filter like the K&N or S&B for one and half to two times the price of a regular air filter. The second time you would have to change the regular air filter, the performance one is paid for. You are saving money from there on out.