Developed for full size steam engines operating on the national rail network and Sentinel S Type waggons where true superheat conditions are experienced on longer hauls i.e. up to 650°F. Locomotives operating under superheat conditions can cause lesser grades to form heavy carbonaceous deposits around piston rings and cylinders. These deposits, which can lead to accelerated wear, are virtually eliminated by the careful selection of base oils, additives and precisely targeted quality control testing.