1970’s M1 5W-20 = HPL 10W-20?

Sep 8, 2005
Just thinking aloud…maybe too much…but go down the rabbit hole with me if you will…
1974 Mobil makes M1 5W-20 oil. From what we know of this oil, it was ‘basically’ a straight 20-weight PAO oil that met 5W requirements.
Back then, J300 wasn’t the same, and cold-temp cranking tests were 5 degrees higher than today, so a 5W was tested at -25, not -30…so by todays standards it would be a ‘10W-20’ in a way.
So, HPL’s 10W-20 oil, although using different base oils and additives, is somewhat similar to the original M1 5W-20, and has similar viscometric properties.
Would love to hear some thoughts on this, especially from HPL.
by todays standards it would be a ‘10W-20’ in a way
You got that backwards. That old M1 5W-20 PAO was actually a 0W-20. NOACK was most likely pretty terrible.

HPL 10W-20 is blended with straight Group III 8 cSt base oil, and it has a NOACK of around 3% - as this was the entire point of blending this - to give customers a lubricant with extremely low volatility.
1974 mobil 1 had a viscosity or 7.5 cst @210 and a viscosity @0F of 1100 cP. pour point was -85F and IIRC from the popular science article from 1976 the noack was around 11-13%. It was a 0w20 but 0w did not exist at the time. If anything the closest HPL has to anything like that would most likely be supercar 0w20.
Interesting, I know ‘0W’ labelling wasnt used on oils in the 1970’s, but I didn’t realize that it didn’t exist - ie didn’t have values attached to it.
I noticed in the PS article that a lot of the cold-weather oils didn’t have grades assigned - Chevron ‘sub zero fluid’; ConocoPhillips ‘polar start DN-600’; Emery ‘frigid go’. In a much older thread on Arctic oils, Molakule set out that a lot of these oils were ‘0W’ oils, but I guess they couldn’t be labelled as such.