If he uses Lawn-Boy oil, the ratio is 32:1. One 8 ounce can to 2 gallons of gas. Other good name brand 2 cycle oils like Stihl, echo etc. will work too. There ratios may be a little higher. Lawn-Boy oil is a low ash oil & will prevent some of the carbon buildup in the exhaust ports. Remember fuel starts to go south after 30 days, so mix it depending on how much you use it. With this said, I don't think that fuel is his problem.