Besides what else has been said you may have 2 oil ports on the motor
and if the blower has bearings 2 oil ports on the blower.

Consider replacing the unit , you may be operating at 40 - 55 %
depending on how it has been maintained and Electrical consumpltion
could be reduced 10 - 30 % by new beltless or VS DC motors. New
furnaces run up to 94.5 % efficient so you may get allot of savings on
a new unit.