Heater blower only works intermittently. I also have an oil leak.
It sounds like the problem could be with the blower motor resistor. If you only have one speed that the motor works on or the blower motor stops working all together you may need to have this replaced. A technician can come and test the resistor and for bad connections on the blower motor. A technician can also look at your oil leak and determine how to fix that as well.