Re: Help!
Whilst I don't like the adapter, the surface area of the open holes appears to be greater than the area of what would be the open area of spigot that screws in.
I know someone who had a builders machinery hire business, they used one diesel engine oil in EVERYTHING they hired out. No oil mix ups. They didn't have tractors though, but the properties of good diesel engine oil work. Mobil sell Super Tractor Oil Universal (STOU) Lubricant, one farm, one oil. One reason - The engineering in Mobil Agri Super 15W-40 meets the diverse lubrication requirements of this equipment which reduces the number of lubricants required and the possibility of misapplication. I use 15/40 diesel oil in my hydraulics and hydraulic drive line of my trencher. Whilst it may not make the grade, and it's best to have the correct lubricant, I doubt you would have caused any damage had you not realized, as it was only a percentage of the main fill.
Kubota also recommend UDT or SUDT in many of their applications for a single use oil for the entire drivetrain/hydraulics, I expect a little something else could make it work for the engine as well....... but perhaps that's stretching it too far as engine design and lubrication requirements change.YMMV