You should lower your car
 

I looked at the most ecomods here and i notice "nobody" mention this mod first of all, in the tuning scene and Motorsport scene we have seen the 80% percent of modified cars using coilovers to lower the car to look better and handling but can we use it for a more aerodynamic car we certainly can if its done properly.
Firstly lowering the car decreases frontal area! So lowering the drag force's
But also you have less air underneath the car will reduce the drag coefficient
Lastly you are going to have better handling so its really the cheapest mod out there but a good one

I can't lower vehicles. The roads where I am are junk and every time it rains the roads flood. I see lowered cars all the time with ripped off bumpers, damaged bumpers from hitting the road where it dips, catching a curb or parking space block.
Plus lowered vehicles ride like forklifts.

When I get the new Prius, I’m going to get an adjustable air suspsneison so I can lower and raise it whenever I want. Permanent lowering just doesn’t work for my ski resort and dirt road driving

Once aerohead got out of my Superbeetle at the Salt Flats, and was surprised that the ground was so close. :thumbup" My limit is 3.5 inches, for the three bump strips to get from Main Street to my place. The tow hook scrapes as it is if you don't cross at an angle.

Get a Type III, the torsion bars are adjustable without affecting the ride.

The panel van could ride right over the 6" concrete stop blocks in big parking lots. The Metro isn't getting lowered, but might get four front/rear wheel spats.

fly in the ointment
 

In a past thread here, years ago we discussed the Audi A2, which was aero-modded by Chalmers University at MIRA in 2012.
One of the tricks they tried in the wind tunnel was was 'lowering.'
The A2 did not demonstrate any drag reduction.
--------------------------------------------------------------------------------------
And I don't know of any economical way that a member or guest could 'simulate' lowering their car, just to 'see' if testing produced a significant enough benefit to justify the expense to provide 'active' suspension.
Just dropping a car, as others have already mentioned, is a recipe for ground strikes, and 'missing', or damaged components.
I have a collection of underbody aerodynamic bits from Corvettes, Firebirds, and some kind of Audis knocked off at a nasty intersection, and Kroger Supermarket driveway ramp in Denton, Texas.:o

VW Type III front torsion bars are adjustable.

When I was in high school we took a classmate's father's red Valiant station wagon into Salem to drag the gut. We'd drive to the end of their dirt driverway, jack the car up and crank the torsion bars down and head for town. Coming back, we'd jack it up and raise it again. Took a few minutes with many hands.

I’m not convinced that lowering a car automatically reduces resistance. Especially on newer cars that have pretty aero undercarriages.
And adding coil overs to lower a car is FAR from an inexpensive mod.

It's just super bugs that aren't equipped with torsion bars in the front and maybe bussies. Everything else aircooled is, more or less, but sometimes not as easy as twisting the ends. There's a wierd process for doing an exact amount in the rear because the splines are odd counts.

A few counterpoints, explain how lowering a car reduces frontal area.
I will concede it should lower drag as most car bottoms are very draggy.
Lowering a car mainly lowers COG, that does not automatically across the board improve a car's handling as there are many other factors at play and it actually may worsen handling.
Additionally, when one does have ride height adjustability, it should be mentioned "rake" is another consideration in reducing drag

Tire frontal area is reduced. So lowering an inch reduces frontal area by about a square foot give or take.