Can you please elaborate further to clear the concept please????
say......5W means viscosity sustainability at -25C Winter, (The oil remains thin enough to get throughout the engine during cold starting at -25C to avoid engine wear)
then 10W means oil can sustain its viscosity till -10C in Winter....
& 40 means .........viscosity sustainability @ 40C (The Oil retains its property / viscosity in summer during warm up loaded operation at ambient 40C)
50C means sustainability of viscosity at 50C ambient in summer....
Please correct me if i am wrong some where as i want to clear the concept.???