K&N or Traditional Air Filter?
To date no MAF sensors that were sent in failed due to the filter oil. In one of their tests they submerse a MAF in K&N filter oil and then take it out and and test it. Results were the same as a new clean one.
K&N does not filter as fine as your stock filter but the combustion environment is a messy one and the burt fuel supplies particles larger than the ones K&N lets pass through.