Originally Posted by tcs

The viscosity of engine oil and gear oil is measured at different temperatures (engines being hotter than gearboxes). 75W-90 gear oil is about the same weight lubricant as 10W-40 engine oil.

After the war when everything was rationed and in short supply, Sturmey said riders could use sewing machine oil in the gears and Vaseline in the labyrinth seals.