Mileage Extenders | Going farther on a tank of gas.

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Mileage Extenders

The subject of fuel is on everybody's minds of late, in large part due to the oil spill in the Gulf, but also from concerns about production peaking and prices spiking. So where do you go to find the latest in fuel-saving devices? You go to hypermilers. They are to the auto industry what the calorie-restriction dieters are to the food industry. They've figured out how to consume the absolute minimum to get where they need to go.

The goal of hypermiling is to exceed the EPA fuel economy rating—and then some. Conventional vehicles can achieve hybrid-like mileage with a combination of driving techniques and vehicle modifications. And better yet, hypermiling in a hybrid can result in 100 mpg.

Some techniques are fairly simple. Others are fairly radical in the pursuit of the most aerodynamic configuration imaginable. But, you don't have to reshape your car into a little teardrop to realize fuel savings. It just depends on how far you're willing to go.

Gadgets and Gauges.

Knowledge is power; in this case, the kind that can take your car farther down the road. The key is to get a gadget that tells you exactly how much fuel you're consuming. The ScanGauge, a plug-and-play tool designed for 1996 or newer U.S. vehicles, gives you instant and resettable fuel consumption feedback to help you modify your driving techniques. This gauge also reads diagnostic codes and other vehicle sensors. Assuming you understand what these readouts mean, you can really fine-tune your quest for maximum fuel efficiency. The MPGuino is a bit more accurate since it measures consumption right at the car's fuel injection system. The downside: It's a do-it-yourself gadget.

Tuning modules are also available that recalibrate your car's engine computer to a more precise setting. Initially developed for power gains, they can do the same on the fuel economy side. What makes all this even better is that there are some performance gains in the process by optimizing the low-end torque and transmission shift-points. Based on real world testing derived from mileage schedules and protocols designed by the Society of Automotive Engineers (SAE), 15 percent more miles per gallon is a reasonable expectation. In dollars and cents, those 15 points would drop a monthly $300 gas bill to $255, which could add up to a significant sum over time.

How You Roll.

New tires and wheels may reduce your carbon footprint, but they'll usually cost a whole lot more than the gas you'll save. However, tires with a lower rolling resistance and lightweight wheels will reduce gas consumption. For that matter, any weight reduction move will help. If you're due for new tires anyway and can spring for aluminum wheels, go for it. A cheaper alternative is to opt for skinny tires, the skinniest recommended by the manufacturer and maintaining optimum air pressure.

Take It Off, Take It All Off.

Interestingly enough, not all fuel-efficient modifications require adding to your vehicle. Many aerodynamic modifications require stripping your vehicle down to its bare, non-wind resistant bones. You've probably seen those diagrams of airflow arrows flowing over a vehicle. You don't want that airflow running smack into a vehicular obstruction creating the same dynamic as driving into a strong head wind.

The biggest culprit for drag is a roof rack. Aftermarket racks are a snap to take off; original equipment racks, not so much. A reasonable compromise is to remove the crossbars and leave the side rails and mounts.

Other aero-obstructers to take off are mud flaps, the right side-mirror (but check with your state's DMV first) and even wiper blades. You can store the blades in your car and re-install when the first drops hit the windshield. The most obvious deletion is the raised wing-type rear spoiler. In NASCAR, the spoilers increase down-force on the rear end, keep the cars from going into the catch fence and improve handling. Your spoiler, however, doesn't do any of these things. It just looks cool, and also consumes fuel.

Aero Add-ons.

Taking another cue from NASCAR, grille blocks reduce the amount of air that enters the engine bay and cut down on aerodynamic drag. The best grille blocks are flush with the outside of the bumper. You have to keep an eye on your temperature gauge, but most grille openings are much larger than necessary for normal driving conditions. In cold weather and with front-wheel drive vehicles, grille blocks allow the engine/transaxle to warm up more quickly and retain more heat.

The underside of your vehicle is an aerodynamic nightmare—air is roiling around down there like a mini cyclone. The solution is a smooth underbelly, so to speak. Some manufacturers are already incorporating an under-tray into vehicle designs. Wheel wells are another area of high turbulence, turbulence that can be minimized with rear wheel skirts. The look is fairly retro but, again, manufacturers are using the technique to improve mileage on new models, so you won't look that geeky. Front wheel skirts have been seen on some concept cars, but since you're dealing with the steering wheels, front skirts are not as simple a modification as those for the rear wheels.

How Low Can You Go?

One fuel saving modification that also looks cool is to lower the vehicle. The vehicle's underbody determines just how effective this move will be in improving gas mileage. Still, lowered vehicles have an improved length-to-height ratio and reduced frontal area and tire/wheel arch gaps, which are all good things.

Truck Bed Fixes.

Tonneau covers can give you a significant fuel savings compared to an open bed. One of the fuel myths, though, is to drive with your tailgate open to release the turbulence. A full or partial tonneau cover does.

Really Simple Savers.

Use the lowest viscosity engine oil recommended by the manufacturer. The saving is not huge, but any savings for no additional cost is a no-brainer. The thinner oil decreases internal engine resistance. Synthetic oil costs more than conventional engine oil, but they have more stable viscosities across a wide range of temperatures. The savings is realized from cold starts until the engine warms up.

Along the same lines, synthetic fluids for both the transmission and differential can reduce friction, causing less energy absorbed as heat into the oil. As with synthetic engine oil, the best fuel savings are in cold climates.

We've also tested a simple fuel enhancer: acetone. No, not nail polish remover, but the 100-percent pure stuff with no additives, available at a paint store. Try adding about two to four ounces every 10 gallons of gas (but be careful not to get it on the vehicle's finish or your hands). It basically reduces the surface tension of the fuel molecules for a better mix with the air and more efficient burn. After spiking the fuel tank on a 2002 Dodge Ram, we saw an improvement of two to three miles per gallon. Not a huge difference, but every bit helps.

The one thing these modifications, along with the more esoteric hypermiling mods, have in common is vehicle efficiency, either in the form of lighter weight, smoother running engine or aerodynamics. At the end of it all, though, the cheapest, most effective change you can make is to take the lead out of your foot.

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