Tips on how to maximize your car's fuel efficiency

BY Jim KerrAuto Tech. Feb 24 04:00 am

While public transportation, bicycles or walking may be an option for some of us, most of people use their vehicles regularly. Probably the most noticeable expense of vehicle operation is fuel, but there are ways to reduce those costs.

The first item on your list for saving fuel is to check your tire pressures. A low tire has higher rolling resistance and uses much more power from the engine. While the recommended tire pressures for your vehicle should be in the owner’s manual or on the door jamb decal, inflating them a couple PSI higher will help decrease rolling resistance. Unfortunately, higher pressures also may make the ride harsher and the tires may wear slightly more in the centre. Check the tires a minimum of once a month or more often if there are large changes in outside air temperature. Air will leak normally from a tire at about one PSI per month, while nitrogen gas-filled tires will lose about one PSI pressure every three months. Never inflate a tire more than the maximum shown on the tire sidewall. It could be dangerous. Check out low rolling resistance tires the next time you need to purchase new tires. Many hybrid vehicles use low rolling resistance tires to help improve fuel economy.

A wheel alignment can also save fuel. Keeping the wheels pointed straight ahead reduces rolling resistance. A four-wheel alignment will ensure that the complete vehicle is pointed straight down the road. If your vehicle is sitting a little crooked because the rear wheels are not in alignment, then the side of the body creates more aerodynamic drag too. Make sure that any chin spoilers beneath the front of the car are in place. Many newer vehicles use a small lower shield to block air beneath the vehicle. This can be damaged by parking curbs or tough snow banks and under car drag increases.

Changing driving habits might be the easiest way of improving fuel economy. Combine trips when possible. If you have to stop at several places, organize so you have the shortest driving route. Avoid quick starts and if you have a manual transmission, shift to the next higher gear as soon as the engine will pull the vehicle smoothly. Avoid stopping unless it is required. Often you can coast up behind traffic and they will start moving before you have to stop. Anytime you use the brakes, you are converting energy in motion into wasted heat energy. Conserve that energy by keeping the vehicle rolling.

Recently a reader asked me if downshifting a manual transmission to keep the engine at higher r.p.m. would save fuel. Not really. Fuel injected vehicles will turn off the fuel injection during deceleration if the engine r.p.m. is high enough, typically about 1600 to 2000 r.p.m. You would save fuel during deceleration but downshifting the transmission would make the vehicle decelerate quicker and you would probably spend more time idling. There would also be increased wear on the clutch and transmission synchronizers. It is better to coast and keep the vehicle rolling as long as possible to save fuel. Use downshifting for when you need additional engine braking on long downhill grades.

Reduce idling time. Most new vehicles have an auto-stop feature that shuts the engine off at idle if the powertrain is up to operating temperature and the passenger compartment is at a comfortable temperature. Come to a stop and the engine is shut off. It starts again automatically when you take your foot off the brake. This feature can save up to 15 per cent fuel in stop-and-go traffic.

Heater performance hasn’t been as good lately? One of the main inputs for determining fuel delivery is engine coolant temperature. If the engine’s thermostat is opening too soon, it takes longer for the engine to get up to operating temperature. You are wasting fuel all that time. Often, a new thermostat is all that is needed so the engine warms up quickly and fuel economy improves dramatically.

Finally, lighter vehicles accelerate easier and therefore typically get better fuel economy. You can’t make your vehicle smaller, but often you can reduce the weight of your vehicle by removing unnecessary items from the trunk. Do you really need that snow shovel or those sand bags there all summer? It may be convenient to keep your golf clubs in the trunk but that costs fuel. Every kilogram less helps fuel economy.

james.kerr@sasktel.net