Cleaning horrible carbon buildup from the pistons and ring grooves. I had tried many things including scraping, soaking, etc. I tried various products including seafoam and Marvel Mystery Oil MMO Soak with no success. I finally tried this Berryman's Chemtool which worked great.

Rebuilding my Saturn 1.9 DOHC engine with new rings, bearings, seals, etc. due to a low compression in cylinder 3 situation. The engine was old and it was time for an overhaul.