Aerodynamics is one of the great frontiers in today's car world, as there are very few areas in anything automotive where one can see effective gains in fuel economy, handling, top speed and acceleration at the same time. While car companies are continuously tweaking tire size and compound, body shape and undercarriage airflow, there are things you yourself can do to enhance their refinements.
A smaller vehicle has less air to displace than a large one. One of the best ways to make a car aerodynamically "smaller" is to lower it with a set of aftermarket lowering springs. The smaller, lower cars now being designed illustrate car manufacturers' move away from higher, larger vehicles like SUVs to vehicles that achieve better fuel consumption.
Car companies have been streamlining the bodies of newer cars to avoid drag by creating smoother body design. Removing items like luggage racks and unnecessary "performance" items like wings and hood scoops can help to reduce the overall drag on your car.
Some of the best looking alloy wheels out there are actually an aerodynamic travesty. Replacing these with smooth Bonneville-style hub caps is a quick way to gain some aerodynamic slickness.
The shape of the side of your car is what dictates much of the airflow at high speed. Installing wheel-cover fairings and side skirts will help to make your ride smoother. If your car bumpers do not have the rounded design of some newer models, a tail cone can be attached to the rear bumper to smooth the airflow from under the car.
Studies are underway at Ferrari and GM to determine whether or not a slightly rough body surface will yield less drag than a smooth one. See the resource at the bottom of this article for some impressive results of recent tests.
