How to Increase the Fuel Mileage on a Jeep Grand Cherokee

Replace the spark plugs with higher-performance models by turning each one in a counter-clockwise direction and securing a new one into the opening. Two things matter the most on a spark plug: heat range and the gap distance of the tip. The Grand Cherokee can use a plug with a heat range of four, but using a hotter or colder plug can change the performance of the motor. For towing, or high-torque applications, a hotter plug will work best. For highway driving, a colder plug range of three will be more efficient. Be sure to "gap" the plug, if using a one-node design, to about .060 mm. If using multi-node, or even quad-tipped plugs, then gapping is not necessary.

Install a clean air filter by opening the air box in the front of the engine and replacing the white paper element inside. A cleaner air filter can increase the air flow to the motor and require less gasoline to burn. An aftermarket air snorkel kit can maximize this air flow, but can cause issues with the computer systems that use an MAF sensor.

Clean the fuel injectors, intake manifold and throttle plate with a commercial spray cleaner. Take the air hose off of the intake manifold by turning the hand-screw on the unit in a counter-clockwise direction. With the engine off, spray a liberal amount of cleaner onto all metallic parts in the air opening. Let it sit for a few minutes, then crank the truck up and run it for several minutes. Shut the truck off and repeat the procedure until the metal is shiny and clean.

Clean the MAF or MAP sensor, if equipped, by removing the sensor from the air hose near the air filter box. Most types are an in-line hose unit that will couple with the air hose with a hose clamp. Turning this hose clamp counter-clockwise will release the hose and MAF sensor unit. Some later models of 4.0-liter straight-six cylinder engines and most 5.7-liter V-8 motors will have a MAF or MAP sensor that meters fuel by constantly testing the incoming air oxygen content. These sensitive sensors can be cleaned with special cleaning spray that does not leave residue. Spray the sensor until it is clean, but do not touch it. Replace it and secure the air hoses.

Add BG-44K to the gasoline tank during a fill-up. This unique cleaner will break up carbon deposits in places the spray cannot reach. It will also clean parts of the fuel system chemically.