LMS recommends Mobil 1 for lubricating mini-mills. I picked up a bottle of
5W-30 and have been using it. I noticed that the oil does not stay on the
dovetails very long and tends to pool on the bench.

In my simple mind I thought: Higher viscosity is needed, something like 20W
or so. That is where I got confused: I looked up the figures for Vactra 2
(being the industry standard for ways etc.). Its kinematic viscosity at 40
deg C is 68 cSt (ISO68). When I looked at the 5W-30 the viscosity was almost
exactly the same. I thought this might be an error on the Mobil page but no,
a similar result came up for 5W-20. To puzzle me further, the 10W-30 is
somewhat thinner at this temp.

The tables at my disposal suggest that the 5W oils should be under 20 cSt at
40.

Before all this I bought a bottle of 15W-50 which was on sale locally.
According to the tables it should be somewhere near 45 cSt but according to
the Mobil product sheet the 40 deg C viscosity is a whopping 131 cSt - about
half way between Vactra 2 and Vactra 4.

What am I missing here? Is this comparison at all valid?

--
Michael Koblic
Campbell River, BC