ISO 68 is a viscosity rating, and no more than that. it says NOTHING about how the oil is built or what it does. You can take that as far as you want to into botique circulating oils, but If you're shopping tractor supply, you want R&O or AW. Nothing else on the bucket. No "tractor fluid". No "hydrostatic fluid". No any other fluid regardless of viscosity.. Either of those are well suited to low powered gearboxes, For high stress stuff (I seriously doubt it in this case) the AW would technically be a "better" oil, but it takes a lot of load to wring out that benefit.
I buy that purpose built and on label. (That, and plain bearing oil, but I doubt that's going to apply to you). You could absolutely use the same hydraulic oil that you use for the gearbox, HOWEVER, it's gotta be reapplied often. VERY often. Cheap, but messy. Vactra no2 is my choice, I got a gallon, which in my world made it priced like any good oil, and should last long enough to still have a little left when the sun swells up and swallows the earth... Why that one? I know too much about modern oils, I get so much of that (crap) to sort at work, this one's easy. It's the gold standard. There are surely some "better", but you're gonna need specific use case information to make the difference show up. Surely there's some not so good, but which ones?. That one's the standard, and I don't care any more than that. It'll exceed my needs at a reasonable price for a premium oil.
I don't think Lucas is the way I'd go for that. We use that for one purpose at work, it is the lubricant, straight out of the bottle, for one particular worm gear box that we have a LOT of, so it's always around. (It does NOT go in engines, ever). Any time I've tried to make "sticky lubricants" out of it, it kinda works out at first, but everything ends up gummy and sticky after some time. I don't mean "tacky oil" sticky, I mean "Cheap duct tape that's been left in the sun" sticky. I wouldn't.
If I was going to cheap out on the way oil, that thing I said about the regular "not tackified" hydraulic oil- If you're dilligent about oiling the ways often, that's valid. Also easier to clean if you're gonna make dust or fine chips boardering on dust (Cast Iron comes to mind but some brass/bronze can get pretty fine) then "not tacky" oil on the ways in that case is a heckuva lot easier to clean up afterwards, even if it isn't your every day choice.
