The gas-to-oil ratio for pre-mix and autoblend outboard motors is 50:1. In the case of pre-mix outboard motors the oil is added to the fuel tank when the tank is being filled with fuel. Autoblend motors have a mounted reservoir that is filled independently, which releases oil steadily.
Modern oil-injection engines use a system similar to autoblend engines. However, there is no requirement to add a small amount of oil to the fuel for the purposes of running the engine. These engines have a reservoir mounted under the engine cowl, which feeds oil into the engine when it is required.