B'nB,
For general purpose lubrication I always used to use diesel multigrade motor oil (it has good cleaning properties as well as lubrication), but since I upgraded my machines to modern ones, I have gone for the standard acceptable oils for use on bedways and in gearboxes.
For gearboxes, a medium grade hydraulic fluid, the name should have a 32 in it. ie. Mobil EAL Hydraulic Oil 32.
For slideways, the same sort of thing but with a 68. ie MAGNA BD 68 Slideway Oil.
They should both cost under 20 pounds sterling for 5 litres.
The 32 keeps the sludge in good suspension, and almost all of the gunk comes out in the oil change.
The 68 is rather a sticky solution, but keeps the ways well lubricated because it stays where it is put.
I don't know if these numbers mean anything in other parts of the world, but are definitely valid in the UK, maybe someone can enlighten us.
Hope this has helped.
Bogs.