The fuel to oil mixture ratio for Evinrude marine outboard motors changes depending on the specific model of engine, and its purpose. Generally, however, motors from before 1958 require a 20:1 mixture ratio, from between 1959 and 1963 a 24:1 ratio, and from then on a 50:1 mixture.
New engines still in their break-in periods require a 25:1 mixture ratio, as do engines used for high-performance and racing applications. Evinrude recommends its own brand of either XD30, XD50 or XD100 grade outboard engine oils for all motors made after 1993. Only two-stroke engines require that owners mix oil into the fuel, as they do not have independent lubrication systems.