Pedro sorry i havent replied xmas party & all. aged or bad fuel was detected in a 15 hp evy i owned 2 years ago, johnson got involved & reluctantly repaired it under warranty. many 2 stroke oils are mineral based & hence go off break down quickly, it will damage the pistons, seals & the fuel system. you may never have a problem all i know is what had shown me on stripping the motor. put another way the 2 stroke oil is used to lubricate the engine correct whilst running, would you use old oil in your car. If you dont use premix fuel [ 2 stroke ] the oil will not deteriate anywhere near as quick. many blokes use hi octane in there motors, bad shit as hi octane has a high temp at detonation therefore making the motor perform at a higher temp exactly the same as if you lean the 2 stoke mix . hope this helps . ed