Many people around here that live on gravel roads even dump oil right on the roads. Others just in their dirt driveways.
Just tell her that it is an oil based sealer that happens to be made of recycled materials and saved money, manufacturing inputs, and shipping.
There are outlets that make environmentally friendly wood deck sealers. Usually the recycled content approaches 98%, mostly from the plastic ring-tops from six packs and old plastic grocery bags. I've heard that it works well if applied correctly, but the mix/ pre-heat is strenuous. The baby seal fat must be heated to exactly 327 deg. before mixing, or it's all for naught. I said screw that, decked my trailer with 11g. diamond plate, never looked back.
I never put anything on my trailer bed boards but if I was going to I would probably just get some deck sealer, put it in a pump sprayer and spray it on. You could even stain it with some oil based deck stain that is ment for horizontal surfaces, spray it on the same way
New Dos Equis commercial- "I don't always coat my trailer deck boards, but when I do, I use the fake crocodile tears of NFL players on bended knee. Stay thirsty, my friends." -The Most Interesting Man In The World.
More than I want to spend, plus with 2 6000 pound axles I am not sure I have seen equipment trailers using metal decks! Maybe the weight of the plate is too much? Thanks for the thought!
What about the "deck over" stuff at Home Depot/Lowe's? You roll it on, it seals and is somewhat of a sandpaper, grippy texture. It would probably run you less than fifty bucks, all in...
If you're actually hauling equipment, the plate would weigh too much and be cost prohibitive. If it's a wood/atv hauler, you could get by with 14g-11g. diamond plate.
I thought about the deckover stuff, but when pallets get pushed on to the trailer, I think it would get tore uo in a hurry. I usually only haul atvs and pellets, couple other things now and again.