Gamo Big Cat with Apex seal - lube question?

I recently got this fine shooting Gamo Big Cat with a Rich from Mich tune, and an Apex seal.
Question I have is...
Since the Apex seal is not what it originally came with, how often should I lube the cylinder and what should I use?
I plan to follow the gun's manual recomendations for the rest but thought I should ask if anything should be done different with an Apex seal installed.

I do know not to use petroleum oils to prevent detonation/dieseling from reading this excellent forum (thanks all...).
I am thinking of using some silicon oil from an R/C car/plane shop since I can't find any Pelgunoil locally and shipping is more than the Pelgunoil costs in a mail order purchase, but I don't know how often to do so.

Thanks
Bruce