I've been rebuilding a couple of vintage motorcycles and had to order a large quantity of industrial USA engine degreaser. Works best diluted 1 part degreaser / 10 part water for washing stubbornly dirty motorcycles. Spray non-diluted degreaser onto metal engine components and the carbon, gunk, everything just comes off. Selling at $5.00 for 1 litre. Collect from upper East Coast road.