my 91 K1500 has a pretty severe oil leak, and up until i bought my C2500 last night, didnt have time to do anything about it. now im left with a pretty big, deep stain on our concrete driveway. anybody got any ideas? tried some engine degreaser, scrubbed it in real good, then took the power washer to it. cut most of it, but still a noticable stain there. what do you use to cut oil stains?