The fuel efficiency of a car refers to the ways in which your car and its engine work to give you the highest miles per gallon of fuel (mpg) possible.
The fuel efficiency of a car is dependent on many factors. Engine configuration -- such as the number of cylinders -- and engine size can make a substantial difference to the overall fuel efficiency of the car. Diesel engines, due partly to the higher energy density of diesel and the greater compression ratio used within the cylinder, tend to be substantially more fuel efficient than a gasoline engine.
These days, additional systems that can increase a car's fuel efficiency are gaining popularity. By far, the most popular of these is the hybrid powertrain. A hybrid is a vehicle that uses a secondary method of producing power to enhance or supplement the power of the vehicle's engine. At present this secondary engine is almost always a battery-powered electric motor.
Other factors influencing fuel efficiency are the weight of the car, the weight of passengers and luggage being carried, its aerodynamic drag and rolling efficiency. For older vehicles it is important that a car has been appropriately maintained. A car that is in a poor state of repair will perform less efficiently and have higher fuel consumption, so if you are buying a used car, it is worth having the car inspected by a qualified mechanic as well as getting a vehicle history report.
What is the significance of a car's miles per gallon figure? Essentially, it is the only number you need to look at when considering the overall fuel efficiency of a car. It tells you how many miles you can expect to drive, allowing for variability in driving conditions, for every gallon of fuel you put into the tank. Car manufacturers now clearly display a fuel efficiency figure for new cars, and comparative figures for older vehicles are easily accessible.
Essentially, today's fuel-efficient car is as small and aerodynamically well designed as possible. Diesel engines and hybrid models tend toward greater fuel efficiency. When looking for a fuel-efficient car, ask yourself what size car you really need. Buying a smaller car generally means better fuel efficiency, but this is little help if the car does not suit your purpose. Remember to look at the miles per gallon -- fuel efficiency comparisons are easy to find and make choosing a fuel-efficient car increasingly easy.