Oak Sleepers - Untreated - What Preservative?

[tnarg999]

Hi
I have some green oak sleepers that I want to use for a small retaining wall. They are untreated and look great when the weather is dry and warm, like today. However, when the British weather returns and they start to get wet, I would like to protect them from rot/fungus/insects etc.

Can anyone recommend a preservative that isn't going to be harmful to pets/children after its been applied? It needs to be clear when it dries so the natural look of the oak is retained.

Thanks for reading.

 

[merlin50]

if its oak do nothing

 

[r896neo]

decking oil is good for them.