Use the gear oil. The regular motor oil will run off the filter over time and so will other thin oils like it, I learned the hard way. A properly oiled foam filter will stop more dirt than a K&N filter.

 

Do yourself a favor, and get any type of foam filter oil. This oil starts out thin to allow saturation, then becomes tacky in a few minutes to properly stop the dirt. Use just enough to work through the filter, ring out the excess, allow to sit a few hours before running the bike. Always clean the filter regularly. I have 3 filters in order to easliy replace after evey ride.