decking stain or oil

My decking need's something on it, looking a tad weathered. We have only been in the house 12 months, I think the decks are around 8 years old, so I have no idea what has been on it before. Reading the back of the can's of decking oil and decking stain, it doesn't really help as to know which is best suited for which job. IE both say tough quality finish etc etc
Can anyone please advise me, I don't want to mess this up
MTIA Steve
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