Leaded gasoline fuel was the predominant type available in the first years of the Wankel engine's development. Lead is a solid lubricant, and leaded gasoline is designed to reduce the wearing of seal and housings. The first engines had the oil supply calculated with consideration of gasoline's lubricating qualities. As leaded gasoline was being phased out, Wankel engines needed an increased mix of oil in the gasoline to provide lubrication to critical engine parts. Experienced users advise, even in engines with electronic fuel injection, adding at least 1% of oil directly to gasoline as a safety measure in case the pump supplying oil to combustion chamber related parts failed or sucked in air. A SAE paper by David Garside extensively described Norton's choices of materials and cooling fins.