Abstract: A mobile undercarriage cleaner design for (but not limited to) use on tractor trailers, buses, dump trucks and other such medium to heavy duty trucks and equipment is disclosed. The apparatus provides a frame to which is attached rotary flow lines that track circles of differing diameters. In one embodiment, one of the rotary flow lines is an upper rotary flow line that carries opposed cleaning nozzles, a lower flow line being a rotary flow line that rotates the first rotating flow line in a circular path. In another embodiment, rotating flow lines have nozzles at differing distances from a center of rotation by providing flow lines of differing lengths. The apparatus is intended for heavy duty, high pressure high temperature environments such as for use by commercial transportation fleets that require the removal of grease, oil, fuel, dirt, mud, salt or other like contaminants.