Rear diffuser?

[aerohead]

Originally Posted by airbiteses

hmm, the question is whether it does anything to reduce fuel consumption. I understand that it doesn't do anything?

Is it possible to improve the rear of the chassis, e.g. the tank, spare wheel?

On internal combustion cars, unless you can route the exhaust system 'through' the body, like Ferrari, Lamborghini, McLaren, etc., it's very difficult to get the underbody smooth enough to allow a proper diffuser to function to full potential.
Dr. Teddy Woll of Daimler-Benz/ Mercedes-Benz wrote about fully-insulating an exhaust system, which 'WOULD' allow for 'encapsulating' it inside of a complete belly pan. M-B won't do it on account of the added cost, and access difficulty when servicing a vehicle, but it doesn't preclude an individual from doing it on their own.