My strategy is to consciously feather the accelerator pedal and avoid deep throttle, jackrabbit starts that get the turbo whistling. Transmission upshift points are below or at the torque peak rpm (1,600) in each gear--unless a hefty load is in tow. Moving nearly four tons of mass from a dead stop to cruise speed is best handled with a lighter foot on the throttle. You can save more fuel here than anywhere else.
When I learned to drive the four-speed '64 CJ-5, my father cautioned, "Drive like you have a raw egg between your shoe and the gas pedal." His generation survived the Great Depression and fuel rationing of WWII. In our era of foreign fuel dependency and peaked oil supply, you can save fuel by 1) coaxing the vehicle to speed, 2) feeding only enough throttle to keep with the traffic flow, 3) executing upshifts at the lowest engine speed without lugging the engine, and 4) taking advantage of the vehicle's forward momentum to reduce engine load. Begin decreasing the throttle pressure as soon as you feel momentum. Once at cruise speed, use only the amount of throttle needed to maintain steady speed. Allow safe passing distances to decrease the demand for fuel when accelerating, and apply the throttle smoothly. You can do this with any vehicle, whether a gasoline or diesel engine.
Find the rpm where your engine provides sufficient torque without lugging. Use this as your shift point when you don't need hard acceleration for safety or a load's sake. Neither lug nor over-rev the engine. Before making mechanical changes, see how much driving technique can improve your vehicle's fuel diet. As the months unfold and fuel prices continue to steer our lives, your street and trail 4x4 does not have to stay parked. Discover the best ways to maximize fuel efficiency and get the most for your fuel dollars. Next month, we're going off-road and saving fuel in the process.
 Stone stock, the 4.0L XJ Cherokee...  Stone stock, the 4.0L XJ Cherokee is just over 3,100 pounds curb weight. Tack on 6-inch long arm suspension, five 33-inch tires on alloy wheels, an ARB front bump with a Warn 9,000 pound capacity winch, and add a Warn rear bumper with tire carrier. Now we're up to 3,800-plus pounds! Also riding higher in the airstream, this vehicle cannot get the same mileage as stock. |  Changing the 3.55 gearing...  Changing the 3.55 gearing to 4.10:1 compensates for 33-inch tires. Mileage and performance would benefit even more from 4.56 or 4.88 gears. The 800 extra pounds of aftermarket components and accessories are like pulling an 800-pound trailer. By gearing lower (numerically higher)--rather than just matching the stock gearing--engine rpm gets closer to the torque peak. |  At left is a TJ Rubicon's...  At left is a TJ Rubicon's 4.0L MPI engine backed by an overdrive transmission. At right is an '87 AMC/Jeep 2.5L TBI four. Both engines lack the low-end torque of the 4.2L six that powered the AMC era CJs and the YJ Wrangler through 1990. They need lower (numerically higher) axle ratios to perform well. While there is some room for improving these EFI engines, greater mileage will come from gearing changes. |
 Wranglers and a Dodge Ram...  Wranglers and a Dodge Ram 3500 Quad-Cab 4WD (the Ram with a turbocharged Cummins diesel) gets upward of 24.3 miles per gallon when not pulling a trailer. Driving technique accounts for this kind of mileage. In addition to correct gearing for tire size, vehicle weight, and load conditions, driving style will improve your mileage dramatically! |  |  |