If you can smell it through the vents 1 of 2 things, maybe both are happening.
1 when moving the air sucked (pushed) in to the cabin is not from the engine bay, so any engine smells are blown under the car and away.
When stopped the engine bay air comes up out of the bonnet and sucked into the cabin.
2 engine bay smells can be from all manner of places, and a through check should be made visually, often oily smells are vapours from the exhaust system and can originate all over the bay but will need a path to the hot bits.
When the engine is cool root around, dry off any wet bits take photos.
Go for a drive, stop, check under the bonnet for signs of oil leakage etc take photos and when it is cool enough not to burn you, have another root around looking for wet bits.
If you find no external oil leakage, you will need to look inside the engine.
Check the inlet manifold for recirculated exhaust.
Check in the cylinders, if you can for signs of burnt oil, turbo inlet and depending how far you want to go, the outlet.
If you have a dpf and or cat, smoke can be revived from the exhaust.
Noses are really sensitive, you may find only small amounts of oil being burned are easily noticed
