A new technique termed the “fixed sleeve” method has been developed to measure the instantaneous friction of the piston and ring assembly as a function of crank angle. This method is a derivative of what has been termed the “moveable bore” method. Results are presented for friction determinations on a 4.1 litre gasoline engine for motoring and firing operation at a variety of speeds, loads, and engine temperatures. The effects of liner surface finish, piston mass, and finally removal of various piston rings are reported. The technique appears very promising for rapid evaluation of piston, ring, and liner variables.