Monograde 85w140

[supercity]

I noticed the other day an 85w140 with a VI of 100 which made me ponder if this was indeed a SAE140 that just happened to meet the requirements of an 85w.Or maybe it was a multigrade with a very low VI. I have also noticed synthetic Mono 50 transmission oils with a VI up around 130 while 75w90s may only have a VI about the same. So what exactly is a Monograde these days? Something without VIIs or something that does not meet a w number?

 

[dparm]

Modern basestocks are getting so good that monogrades often qualify as multigrades. The president of Renewable Lube told me about this phenomena, and you even see it in Red Line products too (their race oils).

 

[Greasymechtech]

It's whatever the blender puts on the label.
SAE J306 covers gear oil.
If a monograde is qualified and labelled as a multigrade, then it's not a monograde anymore.

 

[MolaKule]

A monograde is usually made with a single base oil such that the viscosity of the single base oil is within the kinematic viscosity range of that weight.

For example, if I were to use a 20cSt PAO@100C or an equivalent viscosity mineral oil I could call it a 90 weight monograde.

For multigrades see:

Gear and Lube Technoly Part I

Gear and Lube Technology Part II