Magic
 

Ok, for months my 04 D2 has been leaking oil - about a 2" spot after stopping, you can smell it burning when you get out. We traced the leak to what appeared to be the valve covers so we replaced them, it still leaked. I was going to really do a radical search when I changed oil next but as of the last week it has magically stopped. Never heard of such a thing have any of you??? I did use the newer rubber valve cover gaskets so maybe that did something to take effect after miliage - I simply do not know. PS I did check and refill the oil and still no leaking

99% of the time tightening the valve cover bolts stops the valve covers from leaking.

Believe it or not but new gaskets can leak until they soak up the oil and swell to a larger size.
You may also notice this effect if you change brands of oil.

All D2's came with rubber v/c gaskets. Make a point of tightening the 2 lower bolts at every oil change and they won't vibrate loose and leak again.
By the way, you can power wash your engine to get all the old oil off, it won't hurt a D2 to do this except if you have the original grey plug wires and they will leak and cause a misfire for a few minutes.

And what will it hurt on a D1?

Nothing as long as you dont have a dizzy or get the ECU wet, on the DII the ECU is inside the passenger cabin and non of the NAS versions have a dizzy.