steved, you seem pretty passionate about not liking FF. Sounds like you have plenty of experience with it, probably more than I. I've been in New England most of my life and I've been fighting rust for a long time. I've also been a mechanic most of my life so the fight is always mine and mine alone.
I know oil can wash off vehicles around here. This is the frame of my Toyota. Six years ago it was needle scaled front to back, painted with Rust-Oleum rusty metal primer, painted again with single stage Urethane, then coated with oil. Five years ago it was coated with oil. Four years ago it was coated with oil. Three years ago it was not coated with oil. Two years ago it was parked and was not coated. There is obviously no oil on the frame now. We get large amounts of rain here in warm seasons and in winter salt is applied to the highways in high enough concentration to kill trees on the side of the road. Oil works while it is intact but it does not stay intact here. Even gear oil can wash off, as it did on this vehicle.
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We've had good luck with FF on the the buses. It dries out, yes. But the vehicles are not rusting out like they were before coating, and we're not applying it every year. If that changes or if we don't continue to see good results then I'll stop recommending it. Much of the steel used in building these bodies has no rust protection other than a little paint and a really poor factory undercoat so rust shows up very quickly. Spraying oil on these vehicles is not an option. Even if it were, I'm not interested in annual recoats as I don't have the facility for it. The latest generation of buses can be ordered with a line-x type of undercoat and I really wonder how that's going to turn out. I imagine it will be great until the coating is pierced, then rust is going to eat away at the bus without anyone noticing it.
One thing I've heard of is heating chainsaw bar & chain oil to apply it. I might try it on my own vehicles. It doesn't smell like gear oil and sticks like crazy. The spray cans of chain lube work well but I haven't found 'em for much less than $3.50 a can which adds up when you're doing a complete vehicle.
Mandatory firewood content... I've got a day off so I'm going to head out to the workshop in the barn and burn off more of that Basswood I scrounged last summer.