for a car, what is the consensus on fuel consumption and drag count improvement? can we gather information based on experience in here (not mere text book info, please)

nobody experienced measuring on real car the fuel consumption vs. drag count?

The enthusiasts' car magazine, Road & Track, has for decades tested cars, measuring rolling drag (tires, drive train components), aerodynamica drag, frontal area, etc. Periodically they publish their test methods and the underlying theory. Occasionally (around April 1 of each year), they test huge freight trucks, rail locomotives, boats, etc.

They test cars from all over the world (especially ultra-fast items manufactured in Italy!).

Try enthusiast "auto road & track" in Google to learn more.

thanks! i've searched but could not find much info. Anyway, i guess this magazine like several other magazines are about different makes and the glorified performances including the Cd's. What is more relevant is, however, the information for the same makes and upon improving the Cd through devices or shapes, what improvement in fuel consumption or fuel economy was seen and proven? Those reading this forum and working in the car industry might know this information although never published it... this is a chance to share information without being specific on the makes (but specific on the fuel consumption percents).