This is especially prevalent on the Airbus A320-series aircraft due to the way it's very easy to overfill or spill oil on the APU in a way where the fumes can get sucked into the cabin air.

The only commercial aircraft immune to this issue is the B787 because it does not use engine "bleed air".

Recently flew on an Airbus, but usually fly on a carrier that only flies Boeings. Upon engine startup, there was a extremely strong "burnt oil" odor going through the cabin. Many people were covering their face with their shirt, trying to filter out the smell. I doubt it did anything because I could smell it through an N95.