Cburger...absolutely agree....Oils just make the situation worse
Just leave the teak to weather and clean it every now and again...the greying is the cellulose breaking down due to the UV...this opens the grain and traps dirt...if you put oil
on it, it REALLY traps dirt and needs more frequent cleaning
The ONLY way to preserve the teak colour is to use one of these newer UV protecting coatings like Intergrain...if prepared well and applied well, the coating will last for years....however, if it breaksdown, you have to strip it off and start again.
I'd only use teak for exterior woodwork and I wouldn't put any coating on it, it is naturally non-skid.
Having said that I've just ripped off all my teak decking, excpet for the cockpit
and glassed it....the teak was 20 yrs old and leaking through the million screw holes in the deck