Used on a 13 year old diesel engine that has never been cleaned. There was up to 1/8 inch of dirt on many parts of the engine. Spray 16 ounces of half water and half degreaser on everything under the hood. Avoid contact with painted exterior surfaces. Wash off with water after 30 minutes. The engine looks almost new throughout. This product etches aluminum. Both of my generators have etch marks. Breaks through the previously existing layer of dirt. I think this thing easily became my degreaser overnight.