What is the ideal Pre-Mix Ratio of fuel and oil?
IN February 1978, Gordon Jennings published an article in CYCLE magazine illustrating the results of using different pre-mix ratios of Premium Unleaded Fuel 98 RON and Castrol 40R oil (based on castor-oil or bean oil) in the engine of a SUZUKI PE250 motorcycle. The results indicated, even with many other factors taken into consideration, that changing from a 30:1 ratio to a 15:1 pre-mix ratio (that is, doubling the oil content) reduced the gum varnish on the piston crown, reduced bore scuffing and increased the power output by 15.7%. Before deciding on the best pre-mix ratio to use, for example 33 : 1 (3%) or 50 : 1 (2%), it should be remembered that most modern semi-synthetic 2-Stroke oils have many qualities and additives that allow higher pre-mix ratios while providing excellent lubrication and freedom from gum varnish. It is therefore recommended that the VeloSoleX S 3800 is run at 50 : 1 (2%) pre-mix ratio if using a Semi-Synthetic oil such as Castrol Scoot-R 2-Stroke Oil or a 100
