When oiling an electric motor be sure to use special oil for lubricating electric motors. Other oils could cause excess wear and premature failure.
Pick up a can of electric motor oil. It's specifically designed for electric motor use.
Whenever you have to lubricate an electric pump, bench grinder or other electric motor, don't pull just any oil off the shelf. Instead, pick up electric motor oil, like 3-In-One electric motor oil (about $3 at amazon).
Don't use automotive motor oil! It's too “thin” for electric motors. Plus, it contains detergent. If the excess oil seeps onto the motor windings, it might dissolve the insulation and fry the motor.