Bottom Line
High Performance Diesels
Question of the month: With the high price of diesel fuel how can I improve my fuel mileage?

With the recent nationwide hikes in diesel fuel, the East Coast has seemingly tried to outdo the West Coast to see who could charge more per gallon. Truckers are stuck in the middle. We have been bombarded with questions on how to increase fuel mileage.

First, install the duel fuel line kit on your mechanical NTC Series Cummins engine. This kit will enable the engine to produce an additional 25 horsepower, which equates to pulling mountains half a gear higher. The dual fuel line kit distributes the fuel more evenly throughout the engine. This results in a smoother running, better pulling engine.

Do you have a turbo boost or manifold pressure gauge? This gauge only costs $38. If your truck is not equipped with one, call our shop, get a boost gauge, install it and give it a test run. An NTC 350 develops 18 lbs. of boost, a 400 develops 25 lbs., an N14 500 has 30 lbs., and the 525 has 32 lbs. Why do you need to know this information? Simply, boost equates to horsepower. If you are using excessive boost to move the load, your fuel mileage will suffer. The higher horsepower 855 cubic inch Cummins engines develop 16.5 hp of turbo boost. On level ground, try to maintain your desired speed using about 15 lbs. of boost. You may find it impossible to maintain 75 mph using only 15 lbs. of boost. If that's the case, then slow down to 68 or 70 and see just how much the boost gauge drops. Speed takes power, and that kills fuel mileage. Head and side winds will rob the truck of fuel mileage. When it's windy, slow down and shift into direct gear, don't use a lot of power just to buck the wind.

Liquid filled fuel pressure gauges are also a great gauge to install and use. The lower you can keep the fuel pressure on mechanical engines (while still maintaining a reasonable speed), the greater the success you'll have with fuel mileage. High fuel pressures develop high turbo boost. High boost produces high horsepower. Your truck should have excessive power, but shouldn't have to use it to maintain a reasonable cruising speed.

Lucas Fuel Conditioner also works to improve fuel economy. Many times, we have had reports that the engine will develop three more pounds of turbo boost with Lucas in the fuel. When turbo boost increases without increasing fuel delivery, the exhaust gas temperature will drop by 25 degrees per pound of boost. Lucas also adds lubricity to the fuel, which greatly extends the life of the fuel pump and injectors.

The Fuel Preporator removes air from diesel fuel, increases the horsepower of mechanical engines by 60 hp (electronic engines by 30 hp) and raises the fuel mileage. By removing the 3 percent of air found in diesel fuel, the engine will also pull stronger and smoother. Just think what the Preporator and the duel fuel line kit do together to increase power without increasing fuel delivery. Increased power without increasing fuel results in more fuel mileage.

If you have been following my articles since 1992, you are well aware of the fact that I love horsepower, torque and reasonable speed. High horsepower and torque can result in good fuel economy when used properly.

Remember to keep your air filters clean and make sure that there are no leaks in the charge air cooler. And don't forget to adjust the valves and injectors at least every 70,000 miles. A properly set overhead also translates to fuel economy. If you're still running a small CAM engine, set the overhead at least every 50,000 miles. There are many mechanics in this country that do not know how to properly set an overhead, so choose your mechanic wisely. The life of your engine may depend on it.

Slow down, don't push it and keep your boot out of the throttle until the price of fuel comes down. Also, raise your freight rates. You are the hardest working people in this country and you make all of our lives possible, you deserve to make more money. 

My booklet is available for viewing or download on the web. The address is Our e-mail addresses are, and If you would like our booklet on high performance Cummins diesels, give Aimee a call at 724-274-4080.

The above column is the opinion of the writer and does not necessarily reflect the opinion or beliefs of Land Line Magazine or Cummins Engine Co.