The reason fish oil is effective in protecting against oxidisation is because it does take a long time to dry out

I have a 20ltr drum of pure fish oil I got from a fish meal plant years ago and I use it for inside chasis rails and under floor areas. It works very well and remains "tacky" for years. If it eventually goes hard it needs to be re-applied. No good for painting over.

I reckon the K&H product would of had a low fish oil content.

Not saying it wasn't a good product.

Thanks for the opinions, guys.

Gwendy, my old van was 11 years old when I sold it. There was no rust in the load compartment where I'd fish-oiled the floor, roof and side walls, but the (not fish oiled) securing screws for the doors and trim panels had rusting of the screw heads, even though the screws had been cad plated. Also, the cad plated door brackets had started to corrode badly. Based on my experience, the K & H product was tops and I was really disappointed to find it was no longer available.

So, inspecting the Valvoline Tectyl 506 can, three things were noticeable: 1. the product is a medium brown colour. 2. It is supposed to last about 5 years, then be re-applied.
3. The drying time is 30 minutes. I've used it in an overhead compartment and it was touch-dry in about an hour. Only time will tell whether it is durable.

On a trip to my garden shed, lo and behold, I found an unused can of K & H fish oil! It was still pressurised, so I've sprayed it on all the exposed bolt, screw heads and door bracketry I can see in the load compartment, plus a few in the driving compartment. Touch-dry in about an hour.

Now for the board racks.