In the Gran Turismo series, does the Car Wash washes the car or is it only a fake car wash? I don't remember that the cars got dirty and I don't remember seeing a difference before and after going to the car wash.
It actually depended on the game you played on.
If I remember. the first one does not do anything special. Hence, its a fake car wash.
However, in the second game your car could get dirty, but it never effected performance.
In the third game and up, it starts showing dirt and grime; and that dirt and grime does start affecting performance, mainly in aerodynamics (for example, similar to if you put a spoiler on the back and turn the settings all the way down).
Also, note that car washes got cheaper later in the series, giving way to be more a part of the mechanics of real life.
Not that noticeable, but it does get shinier. The car's paint does get slightly dull if you drive it a lot, so unless you drive that car for hours I don't think there will be any noticeable differences.
The newer games (GT5, GT6) really make the car look dirty, though. Not by DiRT standards of dirty if you take it off-road, but there will be a lot of noticeable dust on the car if you drive it around a lot without taking it for a wash.
in GT1 all that occurs is the shine that a brand new car has will be lost.
It is more obvious in the later GT games, but in the first one it only makes it shiny again.
in Gt1, say you have a car you use a lot, take an MX-5 for example, without racing modifications.
if you compared it to a freshly cleaned one, or one of the same colour in the dealerships, youd notice that the paint is dull and solid colour, itd be entirely red without any shine to it.
all the wash does is refresh the car's shininess in the first game, which looks nice for replays and not much else