It's a Jetta TDI, it uses diesel or biodiesel or sufficiently heated vegetable oil (not yet though) to run. It'll use between 4.6 and 5.6 litres per 100km, so anywhere from around 40mpg to around 50mpg. So far I've replaced the oil and filter a few times, the air filter and the starter. It has travelled over 324000km and seems to be running well, though it is time to take the intake apart for a thorough cleaning.
None really. I'm still testing things and absorbing information. I guess it came with pretty smooth alloy wheels from the factory.
So far I am planning on blocking off most of the upper and lower grilles and installing some sort of wheel skirts on all four corners. Testing so far shows that the car, in mixed driving, is capable of using only 4.3 litres per 100km with only duct-tape wheel skirts and grille blocks. The obvious next step is for more durable modifications. The underside needs a flat pan with fins for ducting and I'll probably extend it out an inch or two for a front, rear and side splitter system. I'll probably also add a land speed style spoiler at the back, a windshield air deflector, zig-zag tape on the leading vertical edges, homemade vortex generators on the trailing edges and maybe even smaller, taller side mirrors.