I changed all mine to mahogany. I hate teak-- it never holds a finish long, does NOT resist rot, and looks green/gray/poop brown/black as only it wills. Now I have the look of an old classic, warm, reddish, alive-looking, all exterior (and some interior) brightwork done in WEST epoxy with the very excellent UV-barrier Captain's Varnish.
For teak, Cetol tends to get the best results with the least work. I would keep a minimum of 3 to 4 coats on it at all times, which means in the beginning of a season you have 6 on it.