Gearbox Oil as lubrication for linear guides and ballscrews

Hello, i'm building a cnc router using ball screws and linear guides and i was wondering if i could use gearbox oil(75W90 / 80W90) or engine oil (5W40 / 10W40 / 15W40). I know that gearbox oil is pretty aggressive on orings and seals as the engine one, but maybe is not so aggressive on linear guides and ball screws. Gearbox oil could be the right choice because of it's high viscosity and stickiness but i'm unsure of the agressiveness.

Anyone has an idea about compatibility?

Why would you want to? The price is nearly the same for a gallon of way oil versus a gallon of motor oil. Don't use used oil either. These are precision ball bearing parts and if you want them to last and be accurate use the correct fluids.

Many systems will use Mobil Vactra No2 but read through the parts you have and see what they recommend. Some of the DIY linear guides actually recommend grease and only need to be greased every xx linear feet of travel, which may be even cheaper than an oil system.

This is the common lube used:
www.ebay.com/itm/1-gallon-Mobil-Vactra-N...p2057872.m2749.l2649

VG 68

I thought about gearbox/engine oil because I have a lot of both, anyway, I have hiwin linear rails and ball screws. I'll read the datasheets for recommendations.

Hiwin carriages should come with grease nipples.
Way oil or hydraulic oil is the oil to use I think if not greasable.

i would stick to a way oil they have additives referred as tackifiers to keep the oil from running off. i used grease at first but had problems with the grease not letting things roll and they slid instead causing problems. the cheap ball screws with the plastic ball returns did not like the sliding caused by grease in my case. Vactra way oil no, 2 and ISO grade 68 should be the same they are just different classification systems. Vactra no,2 is pretty common on the commercial machining centers.

So, in the end gearbox oil is not so bad i would say. For now i'll use gearbox oil for building the machine, and upgrade to way oil in the next oiling or when a long project is ahead.

Thanks a lot guys

i think SAE 9 is another alternative to the other way oils talked about here but don't hold me to that after looking at another chart 20W has the Equivalent Viscosity of ISO 68 and no. 2 way oil from a quick search.