I was cleaning my engine with Gunk (engine brite, I think, but not the foamy stuff) and I tried it on the mastic left by the old hood pad, just to see what would happen. It worked, although since I only tried a little, most of it is still on. I'll have to go back and try the rest (I ran out of Gunk!). But be prepared to quickly wash it off the body, as it will spray and drip down on your fenders, windshield, etc. Since I ran out while spraying the engine, I finished with some WD-40 and used that on the body, immediately followed by presoak, soapy brush, and rinse (I did it at the self-serve car wash so I wouldn't get grime on my driveway).