I used ash from a local sawmill, which is very scarce here in Ohio from the emerald ash borer. I figured if it's good for making baseball bats, it's probably pretty durable for my truck bed.
I used several Cotes of Tung oil, but before I did that I used one of those big propane tank torches and scorched the wood. It really brought the grain out visually. The research I did told me this process was an ancient Asian technique for preserving wood.
Since my truck used to be a fire Dept brush truck I thought it fitting, plus I actually use my truck to haul whatever.....lumber, mulch, firewood, groceries, etc. Best part is if the finish need recoted, just clean and apply.
Lemme see if I have a pic.....if not I'll edit it later and add it tomorrow.