Yesterday I was driving and smoke started emitting from my heater vents and defog vents. In a matter of miles it got pretty heavy- not super thick but very problematic. It caked all my inside glass with an oily residue (reducing visibility) and hot-boxed the whole wagon interior. It even left a hazy film on my driver side mirror as it bellowed out when I rolled the window down. Even after turning of the blower and closing the vents it poured out. This was all over the 4.5 miles to my mechanic's shop.
He (ASE master certified) instantly assumed valve cover gasket which did look oilier than usual. I ordered one and installed it today. I cleaned the oily residue off my glass as best I could. I want to say it didn't smoke for a mile or two but I was driving in the dark. 5.5 miles.It was still definitely smoking but more or less odorless. Again dangerously reducing my visibility from all angles and smoking out my interior.
I deep cleaned my valve cover inside and out so there's no burn-off from that. I want to say the smoke was somewhat less but I can't say for sure since its night time.
My oil last night was on the half-empty side but not too low. The day before this happened I resurfaced my alternator's small wire contact. (Don't know if it's relevant)

I've always had a very mild syrupy oil smell from the vents.
I'm going to ask my mechanic but does anyone have any advice.