I diluted it according to the instructions and put it in a spray bottle. Then I sprayed and brushed everything on a cold 20 year old diesel engine with 220,000 miles on the odometer. After 5 minutes I washed it off with a pressure washer. Amazing difference to see how well it cleans! I've used purple material before but some reviews claim it will corrode components which I haven't seen on this one. I put aluminum foil on the generator and some sensors as recommended in some YouTube videos. Then I removed the aluminum foil and started the engine to dry everything.