90s shock oil measures compared with modern shock oil measures

[AdrianH78]

Hi All,

6 months into my return to model car racing (boy it is tough now) and I am still using my Losi shock oil from back in the day.

My question is, its viscosity measures are 25w 30w 40w etc. whereby modern oil is rated at 250cst, 300cst, 400 cst etc. it seems

So my question is, are they roughly equivalent i.e.

25w = 250cSt
30w = 300cSt
40w = 400cSt

And why the different measure ?!

Many thanks in advanced

Adrian