I tried GreaseMaster on glass for the first time on the Saturn, and I was amazed by its ability to clean glass. In fact, I'd say it's on par with Windex (although I didn't use it side-by-side in a test, and I haven't used Windex in a long time as I use Sprayway). Complete with streak free shine and all. And that's without wiping it down afterwards with a damp cloth. So, the residue is still on there. When rain water hits it, it just washes away the GreaseMaster, and I couldn't see any streaking or anything when it happened on the Saturn. Here I cleaned a really dusty window on my '93 Mustang. Photo: Ryan King, 2006. Click image to enlarge.
Without even bothering to rinse the GreaseMaster off, you can see a drastic difference in this photograph when compared to the one above. I applied it at 400:1 for this. Although I haven't tried it, I imagine the higher the concentration level, the harder it is to wipe streak-free. I know the higher the concentration level the more foaming will occur when agitating. Photo: Ryan King, 2006. Click image to enlarge.