AFTERMARKET: Much Ado About Spoilers
Many cars today come with spoilers--from drag racers to sports cars, to hatchbacks and even SUVs. Some even have them at the front and back. But aside from adding visual interest to a car, spoilers actually serve another more important function: improving aerodynamics.
When it comes to fuel economy, the first thing that most people will look at is the engine. However, there's another element that plays a big role in a car's ability to keep fuel consumption as low as possible, and that is air.
When you're driving slow, or when it isn't particularly windy, then air doesn't really do much to obstruct a vehicle's forward motion. However, if there's a strong gust, or if the vehicle starts to inch toward three-digit speedometer readings, that's when air resistance can severely affect your car's acceleration. That's also when a vehicle's aerodynamics comes into play.
Spoilers are designed to increase a car's grip on the road. Normally, the weight of the car is the only factor that pushes the tires down onto the pavement. Without spoilers, increasing the vehicle's weight is the only way to increase its grip on the road. Unfortunately adding extra weight negatively impacts a car's ability to turn. Replacing the tires with better grip models may also work, but it's a costlier proposition in the long term.
Spoilers 'spoil' aerodynamic lift, which is the force applied by air that pulls the car off the ground. They work like the wing of an airplane, except in reverse. These car accessories generate what's called 'downforce' on the body of the car. This helps the tires grip the road better, which ultimately leads to better handling and cornering.
Spoilers can also reduce drag, the natural reaction of the air to resist motion. The less drag that the car experiences, the less fuel you'll have to burn.
That said, you probably won’t enjoy the benefits of having a spoiler if you're mostly stuck traversing city streets clogged with traffic. On the other hand, if you often drive at high speeds, you are consuming a lot of fuel just to combat drag. In that case, a spoiler's ability to combat drag--even slightly--can have a huge benefit on fuel economy.