Translation:Dw i wedi golchi'r car.
Is there a difference between "golchi" and "ymolchi?"
I think golchi is used when you wash something else (such as the car) and ymolchi when you wash yourself.
So "I am going to wash now", with no object but with implied object "myself", would by ymolchi.
From ym- plus a soft-mutated golchi.
can i say dw i wedi bod yn golchi'r car
I think that would be "I have been washing the car" rather than "I have washed the car".