Tar/oil spot on Window
We went through some muck on country lanes with meltwater from the snow recently, and some of it must have been foully tarry oily stuff, as the front end of our caravan was generously sprayed brownish black. I've got most of it off the fibreglass with Acetone quickly rinsed off once it has done its job, as advised some time ago on one of these forums by a boatbuilder.
But I haven't yet attacked the spot on the window. Not acetone there!
A previous discussion either here or elsewhere - can't find it just now - included the strong view that Brasso used lightly was the thing. I'll welcome suggestions, please, though in general I try to avoid proprietary products, partly for the cocktail of chemicals in them, partly because it's amazing how often a cheap old fashioned household thing can do the job just as well.
Thanks.