I don’t find spoilers attractive and certainly don’t want to pay for one if it doesn’t contribute to the efficiency of the car. Do they really work?
Yes they work; normally at speeds over 90 mph; on lower speeds they are useless and a styling gimmick. When a car is not selling well or close to being discontinued, manufacturers of create a Special Edition, with the usual spoiler or some additional trim and different wheels.
In order to get a more youthful image, some models are called "“Sport”, and they usually have air dams, spoilers, a bigger engine, etc. The front air dam has some usefulness, but is a pain in the neck in areas where it snows and it gets damaged easily.
For US public roadways for all incenses and purposes think of them as cosmetic.
The only vehicles they work for real on are sports cars but at well above legal speeds.
The new wing spoilers work great. I can put my beach towels on one and they’re completely dry by the time I get home.
Seriously, most do nothing for the handling of the car at normal speeds. The guys that write for the magazines claim they can feel the difference on the highway with the Porsch 911 Cararra and the Bugatti Veyron, both of which have automatic spoilers that come up at high speeds, but I doubt if you or I could tell the difference. Regular ones on regular cars are just for looks.
On a FWD vehicle…almost NOTHING…RWD vehicle…yes…but at very high speeds.
RWD vehicle…yes…but at very high speeds AND if the wing is designed properly, not for style (which includes all the ones you see, except possibly the one on the Porsch 911)
PS, a spoiler is not the same as a wing. A wing looks like a wing, stretching across the back of the car, and is (in theory) designed to add downward force to the back of the car, adding traction to the rear wheels. A spoiler is the funny scoop like structure on the top the rear of the car, designed (again in theory) to “spoil” the air flow off the back of the car to minimize the gain of a second car trying to draft behind you.
Also, the little nubby spoilers they put on vans, SUV’s and Scion xB’s are actually quite effective and keeping road grime off the back window. Plus people might think you’re the A-Team.
There are a lot of interesting posts in this thread as well as some statements made that just aren’t completely true. A few posters have claimed that make no difference under 90 mph, and this is false. The problem I think is what people think they are for.
Bill Russell is correct about what a wing is meant to do, but not quite what a spoiler was originally meant to do, other than that it is meant to “spoil” the air.
Spoilers reduce lift by disrupting the laminar (smooth air flow) air flow over the car. Not only does this reduce lift, but it decreases drag. This effect occurs at ALL speeds. It is not ineffective until a certain speed, but if effective at all, is effective at all speeds.
With that said, the difference is minimal at road speeds, which I think is the point most posters are trying to make.
If you don’t like it and it costs money, do not buy one.
The lift produced by a wing is proportional to the square of the airspeed. An airplane that can just only stay in the air at 40 mph can do a four g turn at 80 mph. So, for all practical purposes wings do nearly nothing at normal street speeds.
Wikipedia: “Some spoilers are added to cars primarily for styling purposes and have either little aerodynamic benefit or even make the aerodynamics worse.” I would change that to “Most spoilers”. Bottom line, these things are designed for style, with little or no thought given to aerodynamic effects.
Totally worthless IMHO and get in the way of washing and waxing but my wife likes them so that’s why I spent $400 on one and drilled holes through the trunk to install it. Could have been worse-dealer wanted $800.
If they actually did provide a significant amount of downforce, they would have to be attached to something more substantial than a trunk lid.
Didja ever see the spoiler on the Dodge Race truck? Holey-moley. I like SOME spoilers or air dams. but sometimes they get a bit overstated. Remember guys . . . car styling is subjective, and to each his own. Rocketman
I think the specifics of your question been overlooked by all the answers. Spoilers or wings don’t “contribute to the EFFICIENCY” of a car. They DETRACT efficiency. Their purpose is to increase downforce for improved traction. That means you lose economy by your engine using some of its power from the extra drag and resistance created by the downforce. Speed is irrevelant. If you are moving through the air, there is air resistance, period. It may be minimal, but it’s there. The faster you go, the more the resistance or drag co-efficinet grows, so the more it would effect your gas mileage. SO don’t buy one to save gas, they consume more gas.
Even without incense, they don’t work at normal highway speeds.
;-))
I think that the front spoiler under the bumper works, but not the rear spoiler. Even then high speed is required. My mother’s 1964 Cadillac did not have a front air dam. At speeds over 70 MPH I noticed that steering was too easy, as if the front end was lifting off the ground. When I slowed to 70, I regained the feel of the road. I’ve never had that problem since, though I’ve slowed down in more recent years and don’t exceed the speed limit.
The deck lid spoiler on my Impala works as a grab handle for opening and closing the trunk 
Other then that its purely decoration.