How to Improve the Fuel Mileage of a Ford 6.4 Diesel Engine

by Francis WalshUpdated November 07, 2017

Items you will need

  • Wood blocks

  • Air pressure gauge

  • Floor jack

  • Jack stand

  • Lug wrench

  • Flashlight

The Ford Motor Company enjoys excellent owner loyalty among diesel truck owners. Ford has the distinction of being a high quality diesel truck manufacturer. However, the company has had its problems. The 6.4 liter has had complaints about poor fuel economy in the past. To improve the fuel mileage of your Ford 6.4 diesel engine, follow these easy steps to get better results at the pump.

Park the truck on a flat surface and place wood blocks behind the back wheels and in front of the front wheels. As you do the inspection of the braking system, each tire will be raised, one at a time with a floor jack. Lift the vehicle high enough off the ground to place a jack stand under the frame then lower the weight of the truck back onto the jack stand.

Remove each wheel and tire from the truck. Spin the disc brake rotors or drum brakes to check for rubbing. Eliminate brake friction by adjusting or replacing worn brake pads. Secure the tire and wheel assembly back onto the axle and tighten. Finish checking the brakes by raising the car off the last jack stand and lowering the vehicle to the ground.

Exchange old oil for new in the engine and transmission when specified. Inspect and replace wires and/or cables that become damaged with age. Finally, replace a dirty paper air filter with a performance filter from KNN to increase airflow to the intake. A tune up like this is a proactive measure to improve the fuel mileage of a Ford 6.4 diesel engine.

Avoid extended idling. Idling burns more fuel than starting the engine once you pass the 60 second mark. Turn the motor off if you expect to idle for longer than 60 seconds. Limit the time for warming and cooling the engine prior to driving. Eliminate five minutes of idling a week to gain a mile for every gallon.

Drive in the overdrive gear on the highway. The gear ratio improves gas mileage unless you begin driving too fast. Do not exceed 65 MPH. Driving for extended periods on highways can improve fuel economy if you are able to maintain the same, constant speed. Setting the cruise control can help maintain a constant speed; but if you are driving in changing elevations, it is recommended not to drive with the cruise control on.

Inflate all tires equally and maintain the air pressure as recommended by the data listed on the sidewall of each tire. Over-inflated and under-inflated tires rob your vehicle of mileage. The number one reason for lost fuel economy in any vehicle is improper air pressure in the tires.

Anticipate stops and starts when driving. Rapid acceleration and hard braking burn more fuel than is necessary. Driving at the best engine RPM will increase mileage by burning the fuel more completely, resulting in more miles per gallon. Recognize the behavior of the engine under your direction and how tiny adjustments can result in tremendous fuel economy.


Don’t place things outside the vehicle, such as on the roof rack. Remove all the excess baggage you’re carrying, such as tools and unnecessary equipment.


When Ford's 6.4L diesel engine is operated to get optimal fuel economy, it will run hotter than engines that are not as fuel-efficient. Avoid high temperatures that will damage internal parts by monitoring the engine's EGT (exhaust gas temperature).

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