Smell oil?

00 Subaru legacy GT sedan

132k 5spd new timing belt 5Ks ago with water pump

when I turn the air on(not AC) just vent smell like oil burning?

But when I open the hood there’s no smell under it?

The valve cover gaskets would be the first place to look for a small oil leak. Another possibility could be a heater core leaking antifreeze. It could be mistaken as an oil smell. Is there any dampness on the passenger floor, or is there any loss of coolant?

The passenger floor is dry I don’t think is antifreeze I sure is oil it’s not all the time only some times.
Why can’t I smell it with the hood open? Every thing looks dry under the hood.

Had a problem like this on a 00 Focus,it was a small hard to get to rubber vent line on the backside of the engine-Kevin