A generator having an integral oil tank for an auxiliary power unit (APU) is provided. A gas turbine engine has a turbine shaft extending from an aft portion to a forward portion where it is in communication with a gear box mounted thereto. The gearbox advantageously has at least one oil gravity drain passage in flow communication with a lower portion thereof and is suitable for reducing the speed of the turbine shaft by gear reduction to power an oil cooled generator attached thereto. The oil cooled generator has at least one oil gravity drain passage therein. An engine oil tank is integral with and advantageously removable from the generator and is in flow communication with each oil gravity drain passage making is suitable for gravity scavenging oil from the generator and advantageously the gearbox.