The less friction and resistance (F&R) there is in your vehicle, the better mileage you'll get out of a tank of fuel. F&R can come from a number of things, from dragging drivetrain parts or lugging out-of-round tires to pulling around too much weight. The less resistance to motion, the lighter your fuel bills.
Tire Pressure
Keeping good, equalized pressure in all four of your tires can really improve mileage. We've heard all sorts of amazing statistics about how many gallons are lost each day (if we told you, it'd make you sick) on the freeways around Southern California due to low tire pressure causing the tires to roll with more resistance to motion. By keeping all your tires inflated to optimum pressures on the road, you'll be using less of the earth's petroleum. Go take a look at your tires right now: If the outside tread of the tire is worn more than the middle, you're running underinflated, using more fuel to push around your ride. If the tread is worn more on the outside, the tires are likely overinflated, leading to premature tire wear.
Less Weight Equals a Lighter Load to Push
The less weight your engine has to push around, the easier it will be for the engine to accelerate your vehicle and keep it at speed. This isn't rocket science, just practical thinking. Think up ways you can lighten your load. Maybe you don't have to carry all your tools and camping equipment everywhere you go. We ditched the heavy steel front end of our K5 Blazer for some Glassworks fiberglass fenders (www.glassworksunlimited.com) and lost a considerable amount of weight.
Rid Yourself of Worn Parts
Keep up the maintenance on your rig, and you'll own a more efficient 4x4. Pieces like U-joints can wear out, making them resistant to movement and therefore taking more energy away from the power you put to the ground. If you're using more energy just to turn drivetrain parts, then you're using more fuel to get the same amount of work done.
Lighter Oils
Switching to lighter-weight oils in your drivetrain components (be careful when doing this) creates less drag and therefore lets the engine propel your 4x4 more easily. If you run 20W50 in your engine, try switching up to 10W30. Your engine might need the heavier, thicker oil, but if it doesn't, then you're just sucking power from your overall potential. This goes for gear lube and tranny fluid as well. The thicker the lube, the more drag as the gears try to turn.
Part Time Hubs
If your 4x4 has flanges instead of locking hubs, you're dragging around the front part of your drivetrain all the time. Do you really want that? Of course not. It wears out parts faster and is just more equipment resisting your forward motion. By adding locking hubs, you won't be using energy to spin those two front axleshafts and driveshaft.
Electric Fans
By replacing your mechanically driven fan on the front of your engine with an electric one, you'll be able to make it spin more easily, therefore gaining power and using less fuel. Electric fan kits like those from Flex-a-lite (www.flex-a-lite.com) use electric motors to drive your radiator's cooling fan, and therefore only suck battery juice. And since the power needs of the electric motor is negligible, you're not making your alternator work harder to keep the battery charged, so don't try and debate that one.
Less-Aggressive Tires
Wow, are we actually endorsing this? We hate to say it, but less-aggressive tires are probably a good way to go with the truck you drive to work every day. By switching up to a more street-friendly tread design, there will be less friction between your tires and the road, and the whole package will just roll more smoothly down the road. To really make ourselves sick, we're also going to suggest that stepping down to a smaller tire size will also likely give you good results, as it means less weight to push around.
Get Another Gear
If you're not already using a transmission with an overdrive gear, then put one in. By getting yourself another gear, your overall ratio is lowered and you'll be spinning less rpm to go the same speed on the highway. As long as your engine has enough gusto to push you around in overdrive without being floored all the time, you'll get better fuel economy.
Change Your Axle Ratios
You can also change the gear ratio in your axles to lower the rpm of your engine at a fixed speed. By decreasing the rotations your drivetrain must do to push you a certain distance, you'll conserve fuel.
Better Shocks
You probably wouldn't think of shocks as fuel-saving devices, but if your ride is bouncing up and down instead of rolling smoothly along the highway, you're changing the force on your tires and the tires' force on the ground, therefore leading to more friction and resistance. By adding a new set of shocks, you'll smooth out your ride and make your 4x4 roll more effortlessly down the road.