Oil in air filter/throttle body bolt holes

So I had to take off the air filter housing in order to access the exhaust manifolds due to gasket replacement, but when taking the bolts off that hold the filter housing to the throttle body I noticed that one was very covered in oil. The right hand upper bolt on the B bank was covered in oil, and after removal a small amount of oil dripped out of the bolt hole.

The airfilter is completely clean, does anyone know how oil could have ended up in the bolt hole?

This is not unusual. It’s supposedly the result of heavier fractions of the fuel condensing out on cold surfaces in the intake tract.

Thanks for the response! I am sure you can guess that I wasn’t too impressed when I found oil where there should be no oil, but nevertheless