Originally Posted By: Linctex
Originally Posted By: Miller88
Do they just mix existing oils together?
I've wondered the same thing.
50/50 mix of 5W-20 and 10W-30 = 7.5W-25
No. Each oil weight has a flow range it falls into. This is why the term "thick" and "thin" oil weight came up.
For example, the 30 weight category is between 9.30-12.49 cST @ 100°C.
You can have a 30 weight oil that is 9.35 cST @ 100°C, so almost a 20 weight oil, but is still a 30 weight oil, not a 21.5 (or whatever number it would work out to be) weight oil. Same for an oil with a cST of 12.45, still a 30 weight, just a very thick one, not a 39 weight oil.
Plus mixing viscosity does not always mean the average of the two.