wash and fill up the bus

Hello.
how do I wash and, to supply the bus?
I know that there is a button and you have to go to a store and a gas station, but nothing happens, why?

Once you're in a bus depot or gas station, hit [ALT] to bring the menu up, and the service buttons are at the top. The one with the bus and the blue surrounding it is to wash the bus, the wrench to repair the bus, and the black gas pump is to fill the tank. You may have to come to a stop and set the parking brake first, too. It takes time to both clean and fill the tanks

@ dado,

There isn't any graphical depiction of the bus actually being washed, of fuelled. You'll just see after you've pressed that button, that your bus will be clean. I ran a 13N all night and be morning, is was absolutely filthy. If you're not seeing the really filthy effect on the busses, then it probably won't be obvious to you when you've washed the bus. But yes it does take all the muck off the bus!

Even when you first spawn a bus and wash it, it'll become shinier

thanks a lot