Gas prices keep rising and falling, usually stabilizing at higher levels. There's not much you can do about that, but there are several easy and inexpensive things you can do to your vehicle to get the maximum miles per gallon, adding up to considerable savings over a full year of driving.
There are three areas to consider when trying to attain or beat the EPA mileage claims for your vehicle-reducing parasitic losses, maximizing engine efficiency and changing your driving style. Don't look to any single item for a massive mileage increase. It's a game that requires discipline to find many small improvements that will add up to possibly a 10-15 percent overall increase in fuel economy.
What are the parasitic losses that affect fuel mileage? Anything that impedes the movement of the vehicle down the road such as (tire) rolling resistance, wind resistance, brake drag, wheel alignment and driveline friction. Some items like wind resistance are difficult to avoid. However, tire rolling resistance, brake drag, wheel alignment and driveline friction can all be optimized for a sizeable gain in mileage.
The first place to start any mileage self-help program is to purchase a tire gauge, keep it handy, and use it often. Most vehicle manufacturers recommend tire inflation pressures that are a compromise of comfort and safety. In the vehicles owners manual are listed a range of tire inflation pressures usually to compensate for loaded and unloaded conditions. One of the most important changes you can make is to keep your tires inflated at the highest recommended level. If the manual gives only a single inflation pressure, read the information on the sidewall of your tires concerning maximum safe inflation pressure and add 3-5 pounds of air making certain not to exceed the stated maximum inflation pressure noted on the tire. Keep a close eye on your tires for uneven tire wear. Greater tread wear in the center means too much pressure. If this happens, rotate the tires and slightly reduce air pressure.
Brakes & Alignment
Most brakes drag, but how much is too much? This varies from vehicle to vehicle and it's best left up to an expert at a brake or tire shop to decide, but the good news is that the inspections are usually free. Typical problems are calipers that are not fully retracting because they need to be replaced or rebuilt, or drum brakes that are incorrectly adjusted. While you're there, have the wheel alignment checked and aligned if needed. A modern car typically requires 10-20 road horsepower to maintain a cruise speed on level ground. Improper wheel alignment, a dragging brake or tire pressure that is too low could double the required road horsepower, cutting fuel economy by as much as 20 percent.
So far the items we've talked about are free or are service procedures that you would perform to keep your car safe and operating properly. However, reducing driveline friction is going to require an investment above normal maintenance. The best way to reduce mechanical friction in the drivetrain is to replace petroleum-based lubricants with more expensive synthetic lubricants that have been proven to greatly reduce parasitic drag in engines and differentials. Several NASCAR teams have used zero-weight synthetic oils in their qualifying engines for years because of the horsepower it frees up. Expect to pay up to four times as much for synthetic as petroleum lubricants, however, you get some of that back in longer oil change intervals and longer engine life and easier cold weather starting. This is an area where you really have to do the math and decide if synthetics make sense for you.
Engine efficiency is as critical to fuel economy as reducing parasitic losses. Today's modern computer-controlled, electronically fuel injected engines do a great job at monitoring and adjusting fuel/air ratios for maximum performance and efficiency, but there are still a few things we can do to optimize their performance. Several items need to be regularly serviced. Keeping the air cleaner clean or upgrading to a lower restriction filter element will prevent the choking (richer fuel mixture) effect. Adding fuel injector cleaner to the gas tank every 5,000 miles will ensure that the injectors properly atomize the fuel for consistent combustion and efficiency. Another overlooked component in the fuel injection system is the oxygen (O2) sensor. It is really the brain that tells the computer how much fuel to send to the engine. Replace every 50,000-60,000 miles to keep your engine running at peak efficiency.
Naturally, regular tune-ups that include maintenance of the ignition system and emissions system are very important, but some parts are often overlooked. Engine misfires in today's engines are usually caused by of one of two items: plugged fuel injectors or bad spark plug wires. Misfires take a toll on performance and mileage, no matter how slight. It's a good idea to replace spark plug wires every 50,000-60,000 miles, depending on how severe your driving conditions are.
Driving for Miles
Nothing you do mechanically will have as much effect on fuel mileage as the way you drive. Acceleration requires more horsepower and additional fuel, so how hard and how fast you accelerate determines how much fuel you'll burn. The key is to accelerate smoothly and evenly, staying with traffic, and look ahead so you can anticipate when you will need more power to climb a grade so that you can slowly increase your speed. World famous race driver Jackie Stewart described it best as driving as if there was an egg under the gas pedal.
Another driver-controlled item that has a big influence on mileage is the air conditioning. Air conditioning is one of those parasitic losses that can be eliminated by simply turning off a switch. This is a big one-usually worth 1-2 mpg. Turn on the vents and crack the windows for a huge fuel saving.
We've covered most of what makes sense in the quest for better fuel mileage. There are other major changes such as special gear ratios and torque converters that may provide even larger fuel economy improvements. But when you pencil out the total cost involved, you would have to own the vehicle for 10-15 years to see a return on your investment. A better plan is to trade your vehicle in on a newer, more fuel-efficient model.