Good gas mileage depends on more than engine size and the speed of your vehicle. To add to your ever-growing knowledge bank of random facts that only you would know, here are some of the variables that affect any car’s fuel efficiency, no matter how many cylinders it may have:
1. Aerodynamics – The more effectively a car can “slice through” the air at speed, the less fuel it must use to do so. But a car need not assume a perfect teardrop shape to prove aerodynamically viable. The Ford Flex, for instance, has a boxy shape that might not appear wind-friendly but in fact requires only 8.9 horsepower at 55 miles per hour, while its rivals in the same vehicular class require 9.3 horsepower or more.
2. Weight – Every hundred pounds a vehicle must push along the road can make it up to 2 percent less fuel efficient, FuelEconomy.gov notes. This is one reason a subcompact such as the 2013 Honda CR-Z gets 37 miles per gallon combined while the Mercedes-Benz E63 AMG station wagon gets only 18. Loading a family of five and a trunk full of suitcases into the car will also impact mileage numbers on that summer or winter vacation.
3. Driveline friction – Even the normal operations of a vehicle’s drive system can reduce fuel efficiency, says Tire Buyer. Many system components such as the wheels, crankshaft, drive shaft and flywheel must rotate at high speeds, and the inevitable friction created through this motion leads to more fuel expenditure. Heavier motor and drive components mean greater loss of mechanical efficiency, so vehicles equipped with relatively lightweight components have an edge in this particular race.
4. Rolling resistance – Factors that influence rolling resistance include tire inflation and tread, the grade of the road and the type of road surface. Tires worn down to 2/32″ of usable tread have lost so much gripping capacity that they not only reduce fuel efficiency but also pose a safety hazard, according to TireWear.org. Under-inflated tires create unnecessary friction against the road surface, calling for more engine power to maintain a desired speed. Even a perfectly inflated set of new tires, however, can’t grip a loose surface such as gravel as efficiently as they might a hard asphalt blacktop. An extreme grade works against against you but only when going uphill. The downhill run on that same hill places gravity back on your side, enabling greater fuel efficiency to make up for what you lost on the ascent.
5. Stopping and starting – Whenever a vehicle starts from a dead stop, it must overcome inertia to get rolling again, and this involves expending extra fuel to gain that initial forward momentum. Idling at stop lights also burns fuel, but Ford has introduced a solution to this challenge on its Fusion line of cars. The maker’s “Auto Start-Stop” system automatically shuts the engine off when the car brakes to a full stop, starting itself up again when the pedal is released.
Want to cover all your fuel-efficiency bases? Follow sound preventative maintenance practices, observe fuel-savvy driving techniques and roadway selections, be mindful of weight issues when packing, and consider new technologies that might help you spend less money at the gas pump.