Have 08 supercab, am getting "oily smell" in cab with fresh air intake on, only at idle. I have taken the truck in several times for what I think is a blend door issue....70-75 the temp will fluctuate a lot..blow cold then warm. My truck has the electronic temp control.
Dealer tells me the blend is supposed to work like that....right!
Anyway back to the smell, I have looked all over the engine and cannot find a oil leak and the smell is not really like oil burning just the smell of oil on a hot engine.
It is not exhaust, the service writer said the tech thought it might be heater core....no sign of moisture and it does not smell like coolant. Anybody having a issue like this?

 

No fluid leaks? Push the 'Recirculate' or 'Max' button and forget about it. Whatever it is is coming into the HVAC outside air pickup. Have you changed your cabin air filter if so equipped?