* Over- or under-gearing your truck will make the engine work outside of its peak efficiency range.
* Ensure that the spark plugs, plug wires, cap, points, and rotor are all clean, not cracked or worn out, and are set correctly. Dirty spark plugs can misfire; make sure you clean and gap them right. How's the ignition timing?
* Some people believe if they drive with the tailgate down, they'll get better fuel economy. No sense trying to convince them otherwise. But we've found no difference.
* Swapping out the stock engine-driven fan and fan shroud for an electric fan (such as one from Flex-a-lite, www.flex-a-lite.com) is designed to keep the engine cooler as well as get rid of the drag from the stock fan, which in turn can bump up the mileage.
* Adding Overdrive to the transmission will lower the engine rpm to help keep it in peak range. You can get a kit from Advance Adapters (www.advanceadapters.com), such as the Ranger Torque Splitter Two-Speed Overdrive for the manual trans, which adds a gear between each gear already in the transmission, essentially turning your four-speed into an eight-speed. It's one of the priciest fuel-economy fixes, but the Overdrive kit will also help with towing and offer more gear choices off road. Also, higher gears and lower speeds equals an engine turning slower. Less gas is needed to do that.
* Think swapping in a bigger engine is counterproductive to getting better fuel economy? If you've put larger tires and a lift kit on a rig that has a small engine, it might be working harder to maintain freeway speeds. But drop in a V-8, and it will probably improve your mileage because it's better matched to how you've outfitted the truck.
* Have an in-vehicle entertainment system Must be nice to be rich. Shut it off when no one is watching. It's a drain.
* Add a performance (calibration) chip that can reprogram your vehicle's computer, adjusting ignition timing and the air/fuel mix for performance that's suited to your driving style, whether a power programmer or control module. (Try BD Power, www.bdpower.com or JET, www.jetchip.com.) There should be an increase in both hp and gas mileage, among other benefits. Consider it if you tow.
* Keep the tires at the recommended air pressure. You can reduce fuel economy by 3.3 percent if you don't.
* An exhaust system or headers (such as from Borla, www.borla.com) can improve performance, because when air runs into resistance, it can build backpressure. You don't necessarily need the biggest tailpipe, though.
* Big tires equal more rolling resistance. Skinny tires create less friction on the pavement. Do you need a 44-inch tire on the street? More weight requires more effort to move, and lowers your fuel economy.
* vMake sure your speedometer is correctly calibrated, otherwise you have no idea about your true fuel economy.
* Airdams, spoilers, and tonneaus provide better airflow, less drag. The smoother the body of the vehicle, the better the mileage.
* If your wheeling is seasonal, consider taking off the big rubber for something more street friendly until you're ready to hit the trail again.
* Drive someone else's vehicle. Or if they figure out your master plan, maybe sign up for a co-op (check out www.zipcar.com); gas and insurance is paid for.
* Don't accelerate hard or gun it. That wastes fuel. * Use cruise control on most roads. It keeps the mph and internal activity steady.
* Lighten the load. Clear out the bed of spare parts and tools, and clean the interior (those McFood wrappers add up). For every 100 extra pounds you're hauling, that's 1-2 percent worse gas mileage you're getting.
* Make sure your camper or bedcap is level with the top of the cab. It's aerodynamics again.
* Burnt fuel leaves behind all sorts of garbage that can get stuck in the combustion chambers and valves. Using an additive (like Justice Brother's Fuel Injection System Cleaner, www.justicebrothers.com) can be poured into the tank to help remove carbon and other deposits. To slow the burn rate of combustion, there are also octane boosters.
* If you bolted in a larger axle, don't worry about any additional weight from that. Think more about the tire size and final gear ratio combo. Get technical support about choosing the right gearing if you're not sure (such as from Reider Racing, www.reiderracing.com).
* Four-wheel drive puts power (work) to all four corners instead of propelling your vehicle with just the rear two wheels. This means more drivetrain turning, and therefore more drag on your engine. It's not rocket science.
* Bought a new truck or stuffed in a new mill? Don't forget that there's a break-in period, so you may not see its top fuel economy until as many as 5,000 miles on a gas-fueled engine, and up to 20,000 miles for a diesel.
* Don't speed. Every 5 mph over 60 mph can cost up to $0.21 more per gallon.
* Aluminum wheels are lighter than steel wheels, and every pound of weight added decreases fuel economy.