The K&N oil for use in their cleanable metal filters with the cotton element isn't suitable for foam filters - it isn't sticky and won't trap the dirt in teh coarser foam element. Some filter oil solvents will degrade the foam - Castrol I would avoid.
If its a foam filter you could use motor bike air filter oil or K&N air filter oil avaliable at Repco/Supacheep ect.
Make sure it is foam air filter oil.
The K&N oil for use in their cleanable metal filters with the cotton element isn't suitable for foam filters - it isn't sticky and won't trap the dirt in teh coarser foam element. Some filter oil solvents will degrade the foam - Castrol I would avoid.
motul foam filter oil works well (on foam motorcycle air filters)nice and tacky and doesn't degrade the foam
available from most M/C shops