Not oil.
Oil is the lube for the classic tippmann guns such as 98s, a5, x7
But for the 'flex valve' generation - x7 phenom, Tpx, TiPx it's grease
The obvious answer is to use tippmann grease, I believe it is a Dow 33 grade grease so any of the appropriate paintball greases could be used if you already have some
Pick your favourite paintball retailer and ring to see if they have tippmann grease, failing that bz certainly ought to as they are tippmann techs!