All Purpose Cleaner. Engine and Interior Cleaner PROCHOICE® ALL-PURPOSE CLEANER (APC) is an alkaline-based cleaner that is built to be gentle on most cleaning applications compared to conventional acid-based cleaners. PROChoice® APC has a very high dilution ratio that makes it one of the most economical solutions from cleaning dirt and grime to interior and engine compartments. Dilution Guide: (Engine/Interior) Engine â–º 1:5 Interior â–º 1:10