Smelling burnt oil from air vents

I own a 2001 Audio A4 Quatro 1.8t with about 60,000. It has been garage kept and I am the orginal owner. I have not been in an accident and always got my oil change on time. Audi recommends with their oil an oil change every 10,000 or around that. I dont use their oil because some of my mechanic friends stated they dont believe in that 10,0000 change but they like the 3,000. So,I change mine every 3,000. I have been smelling burnt oil emitting from my air vents. I dont see any oil on the ground. I had a mechanic look at the engine and he did not see any oil or dry oil any where on my engine. He also stated that checked the computer in the car and it showed no problem. Can you help. Also, should I be using the Audo oil to change every 10,000 miles- Thanks Audi owner

Not familiar with Audi engines, but with an oil change frequency of 10k miles, they are certainly suggesting that you use synthetic, rather than conventional motor oil.

If the manufacturer suggests synthetic oil, then that is what you should be using. Not necessarily the same oil they sell at the dealer, but you should use synthetic oil.

With synthetic oil, 3k mile oil changes are unnecessary, even if you drive mostly short trips. You are wasting good oil. 3k oil changes were common 20 years ago with cars that used conventional oil. Prior to that, we changed at 2k miles.

With synthetic oil, I would suggest something like 5k miles if the car is used exclusively in town, and 10k miles if it is used only on the open road.

As for the burnt oil smell, that means the leak is most likely above the exhaust pipe somewhere. It may be that the oil can get from the valve cover gasket to the top of the exhaust manifold without being in a spot that is visible to the mechanic. This is more of an annoyance than a problem, but I’m guessing that you will be getting a new valve cover gasket at some point.