So why do 5W-40 oils typically have higher viscocity than 0W-40 at higher temperatures? (eg 100C)?
Remember you did ask
For the Saybolt Viscometer, the amount of oil to be measured is 60ml. There's two types of Saybolt Viscometer, Type-I is called the Furol Viscometer, Type-II is called the Universal Viscometer. "Furol" is a made-up word based on fuel and road oil ie, that's what's used to test the oil you put in your car. The Universal Viscometer is used for other industrial lubricants and oils, and has largely been superceded by kinematic viscosity methods those performed using the type-I system.
They measure time for a predetermined temperature. Under these classifications, the winter grades of 5W, 10W and 20W are determined by the oils' viscosity at 0° Fahrenheit (-18°C), while grades 20,30, 40 and 50 are determined by its viscosity at 212° Fahrenheit (100°C). Those are the predetermined temperatures.
HAD A GOOD RUN TODAY AND ALL IS WELL