I'm sure that stain is oil bassed, but how well will it hold up to deisel fuel and gear oil spills? I refuel sometimes on my trailer(if pulling it by a station, or from my 5 gal container) and bushhogs etc leak from time to time, just thinking out loud. Also when i loaded my disk harrow on the trailer and moved it around the disks gouge the wood out, thereby taking a paint with it. Why not just buy treated wood for your trailer a 16 foot trailer could only cost what another $50 to get treated wood. I know treated is not forevr but a heck of a lot longer than untreated that mildews after the first rain.