How to Improve Gas Mileage on an F250 5.4 Engine

The 5.4-liter, eight-cylinder engine is available in numerous Ford trucks, including the F250. Eight-cylinder engines are well-known as gas guzzlers. Improving the mileage on a Ford F250 without incurring exceptional costs requires increasing the flow of air into the engine and the quality and consistency of the spark. Quad-head platinum or iridium plugs provide stronger sparks with greater consistency. Lifetime, high-flow air filters drastically improve the amount and quality of air flowing into the engine. Both options can increase your mileage by 15 percent to 20 percent.

Replace the air filter with the high-flow air filter. The air filter is on top of the 5.4-liter engine. Release the retaining clamps and pull the filter carrier out. The new air filter fits into the stock carrier. Insert the new air filter and slide the carrier back into the housing. Press the clamps back into place.

Remove the air intake that sits on top of the engine. The air intake is the large, plastic housing that says "5.4L" on top. Use a socket wrench to remove the three bolts that hold this into place and a screwdriver to loosen the clamps that hold the intake hose to the intake housing. You will be able to see the coil packs for the spark plugs, which are black cylinders. You will see eight total.

Remove the retaining screw holding the coil pack in place, and wiggle the coil pack free of the spark plug. Insert the spark plug socket and socket wrench into the hole beneath the coil pack to loosen the plug. Twist the plug counterclockwise to remove it. You will need to use a combination of extensions and swivel-arms to reach the plug.

Attach the new spark plug to the spark plug socket and insert the socket into the spark plug hole. Twist the plug clockwise to tighten it down. Reattach the coil pack and retaining screw.

Repeat Steps 3 and 4 for each spark plug. Work one plug at a time so that you do not mix up the plug wires.

Reinstall the intake housing and hoses in the reverse of their removal.

Take the vehicle to a muffler shop to be fitted with wider exhaust pipe and a high-flow muffler. Widening the exhaust pipe and muffler allows for smoother release of exhaust gases and lower consumption of fuel. The costs are slightly elevated compared to air filter and spark plug replacements.