I found a study which puts oil bath and paper elements into perspective in a test engine. What I don't agree with is that they ran the oil bath air filter with the improper amount of oil. They filled the oil bath air filter to only 50% of the fill level to 'accelerate the test'. What??? So if you never maintain your air filter it won't work... I agree with that. BUT they never used this 'accelerated wear' on the paper filter. So they, in effect, tested a new, high efficiency paper filter against an improperly maintained oil bath filter and determined that the improperly maintained oil bath air cleaner was not as efficient. DUH.
https://books.google.com/books?id=Q...%20oil%20bath%20air%20filter&f=false
