Treating a Merbau Deck

Hi

I have laid a 40sqm Merbau deck. I brought the decking second hand, it had never been treated and had greyed and some cracking, I ran the whole lot thru my thicknesser, then routered each board and it has come up pretty well. I have gotten rid of all the greying but still have a little cracking in some boards. I was trying to decide what is the best thing to treat the deck with. i thought about oiling the deck to get moisture back into it and prevent any more cracking, i dont know whether that is the best thing to do or whether to use a product like Spa n Deck. I just want to prevent the timber from cracking.

Will Spa n Deck put moisture back into the timber?
Will Spa n Deck protect better then Oil
If oil is better what would you recommend?
Which is better Sikkens or Spa n Deck or Oil

I need help

Scott

Has anyone used Ultradeck, how does this product compare to Spa n Deck or oils such as Organ Oil or other good deck oils