Why use a different oil in each season? If the winter weight is the same (5W), the weights will be the same when cold… Operating temp is the same in winter/summer. Unless people have analysed the fluid dynamics of the oiling system of the engine, then I would not deviate from manufacturers guidelines. Unless you conduct a scientific comparison showing more wear with the lower viscosity oil, it’s all just circumstantial.
1. The weights are not the same when cold no mater what your number say. If you do not trust my test do your own. Store oil at -10 and pour through small funnel and see 5w40 is thicker. Very visible thicker not just tiny bit . 2. Operating temp is not the same winter and summer. That is completely stupid to even say. Fit an oil temp gauge and see. I fitted one so i see whats my oil temp and I also have one for water. 3. How do you know i did not conduct a scientific comparison? I actually came to this conclusion after years of experimentation. You do not have to follow my advice . Do what ever you want . Do your own testing. Fit your own temperature probes in oil pan and monitor in summer and winter and write tables and do flow tests and lubricity test on different temperature yourself like I done myself . Im not here to tell you what to think. And you are here in my youtube and should respect my opinion as mine.
