I use denatured alcohol...same thing I use on tape heads....bought at a paint or good hardware/box store.  Works great, but I don't use it as a maintenance thing for vacs...just cleaning up something old or battle weary. There's times though that denatured alcohol is not strong enough. From there I go to MEK......but it's really toxic and melts plastic very easily. Usually, I have to buff the plastic afterward to remove the streak marks from the pad or rags I used.  It's only as a last ditch effort. 

Kevin