By Jim Kerr
The rising cost of gasoline is creating a new awareness of what we drive and how we drive. But while purchasing a new small economy car will have an impact on the amount of fuel you use, there is a lot you can do to improve the fuel economy of your existing vehicle.
One technique is to avoid rapid acceleration and combine short errand trips into a longer drive that can accomplish more tasks. Keeping your vehicle in good operating condition by having the engine tuned and tires inflated to the correct pressures will use less fuel. All these strategies work, and work remarkably well. It is fairly easy to improve fuel economy by ten per cent just by changing driving habits.
There are accessories that can help us change our driving. They range from simple devices that turn on a green light when driving in an economical style, to complex factory-installed trip computers that will calculate the average vehicle speed, fuel economy and distance travelled. Other devices fall between these limits, and may indicate economy and average driving speed based on data we enter into the module. All of these devices will help save fuel if you use the displays to change driving styles and maximize fuel economy.
One of the simplest tools that can be used to improve fuel economy is a vacuum gauge. These gauges can often be purchased for only a few dollars at a salvage store or discount auto parts outlet, although you can spend more if you want a fancy looking gauge. Add a length of rubber hose that runs from the gauge to a port on the engine's intake manifold and you have a simple economy gauge. This setup won't give you actual readings on fuel economy. The trick here is to keep the vacuum gauge reading as high as possible. That will improve your fuel economy.
When you accelerate quickly, the throttle is opened further. This lets more air into the engine and more fuel is injected in proportion to the amount of air; keeping the vacuum gauge reading high means that the throttle has not been opened far.
When driving on the highway, the vacuum gauge can work just as effectively. Driving at speeds so the vacuum reading is high will maximize fuel economy. Of course, keeping up with the traffic flow is important, as is getting to your destination in a reasonable time. You may be able to get better fuel economy at 70 km/h but who would want to travel at that speed across the country! The faster you drive, the more fuel the vehicle uses. Estimates are that fuel consumption increases about 10% when a vehicle is driven at 110 km/h instead of cruising at 100 km/h. Travel faster than 110 km/h and fuel consumption typically drops significantly - not to mention the increased costs of speeding tickets.
Reducing engine speed helps save fuel. Overdrive transmissions have helped a lot, however, there are times when it is better to shift down to a lower gear to save fuel. If you are hauling a heavy load or climbing a long hill, the vehicle and engine speed starts to slow down. Drivers compensate by stepping on the gas pedal so the engine makes more power to keep speed up, but this drops engine vacuum. Fuel injection sensors on the engine monitor engine vacuum, and when the computer sees a lower vacuum, it injects more fuel so the engine can handle the additional load placed on it. By shifting down one gear, the engine now spins faster, the vehicle has a gear advantage to help pull it and engine vacuum stays higher. Shifting down when loaded can save fuel.
My father taught me a lesson on how to drive on slippery roads and the same technique works to improve fuel economy. Drive as if you had a raw egg between your foot and the gas and brake pedals. If you don't break the egg, fuel economy will be up. Break the egg and you are driving more aggressively - fuel economy drops. Now I only have to convince my son it really does work!
Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC).
