Has anyone used hard wax oil finish such as Fiddes, Rubio or Osmo?

[ChuckM]

Could/should I use any of these products over polyurethane? Snip.

No, if you go by this article:https://www.thedecoratorsforum.com/osmo-oil-review/ (I disagree on not using Osmo over stain. I did it with the chairs, and nothing went wrong.)

But why do you need the Osmo if the wood is protected by the poly?

I use either the Osmo or the poly/arm-r-seal, but never both.

 

[Crazyraceguy]

I would think that you would want to go the opposite direction, if you needed both. The poly is a film finish that dries on top of the wood. The oils soak into the wood and cure more slowly hardening the fibers too.
The oil can't soak into the poly, so it will lay on top and probably get sticky, never curing properly.
That is what makes repairing oils it so easy though, scuff it up and reapply.
A film finish is generally more durable, so what did scratch the oil, might not on the poly, but repairing the poly takes much more work.
Oils aren't as resistant to water, alcohol spills, or wear like a kitchen able top, so a film finish over it can help with that.
"They say" these newer (at least in the US market) are indeed tougher than the BLO or similar that we have had for years, but I have very limited experience with them. I used Rubio once, on a small keepsake box. It was/is great, but gets virtually zero wear.

 

[mrFinpgh]

Generally, you would not use these in combination with other finishes at all, as they are supposed to be applied to raw wood and one of the main components is wax. They are all intended to be 'in the wood'/'just barely on the surface' finishes.

If you wanted an oil under a poly and wanted to avoid the drying agents, you could go with Tried and True oil, which is a real polymerized linseed oil. It takes a little bit to cure, but it is nice.

If you wanted a wax on top of your finish, then plenty of options are out there that would be suitable.

I applied Rubio to my floors before moving into my house 8 years ago. I followed their instructions to the letter - sanding no higher than 120, screening, vacuuming all the dust up, and applied a single coat with a red oad, buffing off the excess with a white pad and then a towel. I have admittedly not done a great job keeping up with the cleaning, and have yet to reapply any maintenance oil. The finish is holding up quite well, with the exception of the area right in front the stove. I would imagine half an hour of effort could bring that back to 'normal'.