Hello,

We are currenty overhauling our turning and milling machines.
According to manufacturer the gearbox oil should be N68.
I assume this means ISO VG 68.What is the N?
The question is will any 68 oil do? we have ESSO NUTO H 68 and turbine oil 68.
Can anybody advise please.

N68 appears to be a brand name from Exxon Mobil. Univis N (followed by the ISO#)THey claim exceptional purity in this product. Here is a PDF link to the product.
http://www.imperialoil.ca/Canada-English/Files/Products...AENINDESUnivis_n.pdf

AS your manufacturer seems to require an exceptionally clean and stable product (N68)Turbine oil or the Exxon N68 should work for you.
Wait for other forum members to concur or provide additional information on this subject.
Hope this helps