On Sat, 17 Feb 2018 15:09:03 -0500, Frank "frank wrote:

On 2/17/2018 2:53 PM, wrote:
What does 10w30 mean on oil cans? Is it 10 winter and 30 what? And how is it determined?

Was going to type this but easier to clip from google hit:

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.

As this chemist understands it, there are polymers in the oil that
lengthen with temperature causing the viscosity increase.

I always found in interesting how viscosity changes in oil labeled as
such. What happens to 40W or 90W gear oil? Gear boxes and vehicle
differentials go from cold to hot pretty quick...