Spirit of Ecomodder drag index comparison
 

Here's where aero-modding gets fun!
The following vehicles all have a drag index equal to,or very close to Spirit's 7.757 square-feet ( 0.7209 meters-squared ).
As they come from the factory,they're virtually,aerodynamically identical.
A very small (think Renault LeCar) vehicle with a large drag coefficient can have the same overall drag as a large,well-streamlined form.And visa-versa.
And it's the visa-versa which has interested me since the Arab Oil Embargo of 1973.
By streamlining the T-100,I've been able to achieve,or exceed the fuel efficiency of some of the smallest mini-cars ever sold in the USA.
Here's the list:
*SAAB 9000 Turbo
*'82 Camaro Z28
*Mitsubishi Starion Turbo
*Porsche 935/78
*Porsche 936 closed-canopy
*Ford Aspire
*'89 Porsche 911 Carrera 4
*Jaguar XJ Supercharged
*Buick Regal CXL
*Cadillac CTS VSport
*Lamborghini Huracan LP 610-4
*'05 Volkswagen Jetta
*Chrysler Sebring convertible
*'86 Ford Fiesta
*Jaguar XJ-S
*Renault 5/LeCar
*Toyota Starlet
*Subaru Impreza
*Nissan LEAF-I
*Dodge Viper SRT 10
*AUDI R8 V10 PLUS
*'14 Corvette Stingray
*'82 VW Passat
*'81 Ford Escort
*Volkswagen Scirocco-I
*'77 Porsche 911 S
*'77 Porsche 928 S
*1924 Rumpler Tropenwagen Limousine
*'07 Hyundai Elantra Touring
*Saturn SW
*'08 Honda Fit
*'99 Subaru Legacy Outback Wagon
*Toyota Camry Solara
*Toyota-Pontiac/Matrix'Vibe
*Volvo 940
*'83 Toyota Celica GT-S
*Mitsubishi i-MiEV
*C4 Corvette (lights up)
*C5 Corvette Z06
*C5 Corvette
*'86 Lancia Thema
*'86 Alfa Romeo GTV
*'86 Ford Scorpio
*'04 Chevrolet AVEO
*Chevrolet VEGA
*'00 Chevrolet Monte Carlo
*'17 Chevrolet BOLT
*'04 SVT Mustang
*'91 Mercedes-Benz S-Class
*Jaguar XFR

It's those mini-cars that suffer most, like the Smart Fortwo (drag area .709 meters-squared): they have to be tall enough to fit a driver, but are short enough that low Cd is all but impossible.

Do you have the specific numbers for those?

Passat/Scirocco
 

Passat 7.714 sq-ft
Scirocco 7.632 sq-ft

Not much reduction in the 'sporty' version.

much
 

yep,it's a game of slow,incremental change,so as not to scare off the customer,dating to around 1926.