Sounds like you could use a large shed?
I have a large shed I'm finally finishing the shelving and off-grid solar setup for. It stores all that junk you were talking about. I usually have two cars in the two-car garage, but when you have 4 cars and only 1-2 of them are operational at any given time (ze Germans really know how to make'm!) something has to give.
I am still mostly working on concrete + cardboard when wrenching, but I have serious plans for a new house and 4-car garage with lift. We'll see if we ever get there.
Things will get a lot better around here when I cut down a few medium trees, and take care of a few other things.
As for washing cars, I feel like finally getting a pressure washer setup will make things a lot easier on me in that regard.