That's simply not true. It IS multi viscosity and that is accomplished by VIIs which stands for "Viscosity Index Improvers". Grades or weights of oil are defined by their viscosity. Multi weight oil HAS to pass both SAE J300 test parameters for which it is advertised to be. In this case the oil has to pass BOTH 15W cold tests and 50W hot tests to be classified as such.
Below is from Bel-Ray
The SAE designation for multi-grade oils includes two viscosity grades; for example, 10W-30 designates a common multi-grade oil. The first number '10W' is the viscosity of the oil at cold temperature and the second number is the viscosity at 100 °C (212 °F). The two numbers used are individually defined by SAE J300 for single-grade oils. Therefore, an oil labeled as 10W-30 must pass the SAE J300 viscosity grade requirement for both 10W and 30, and all limitations placed on the viscosity grades (for example, a 10W-30 oil must fail the J300 requirements at 5W).
I get this Monte. One time they say viscosity and then they say grade. Viscosity is temperature referenced. Grade is what they are rated at. If you take a 50 and measure it at ambient it will be closer to the winter grade number. But the viscosity is related to temp. At 212* a 50 is a 50. At 240* it's still a 50, but its viscosity is much thinner. Still a 50 though.
