Would it be Mobil 1 0W-20, 5W-30 or Amsoil 5W-20 for a car calls for 5W-20 grade? I live in a colder climate and because my work has no underground parking, my car ends up sitting outside for prolonged periods of time, even overnight often times when I have to pull off allnighters at work to meet deadlines. Sometimes, it'll get as low as -40C/-40F overnight here and the winters here are about 6 months long. Some might argue that well, duh, since your car calls for a 5W-20, of course you should use Amsoil's 5W-20, but I'm currently using Mobil 1's 5W-30 because its 0W-20 is not available at all in the city. But just found someone who will be carrying it, along with Amsoil's 5W-20. Now, I'm left to choose and thought I'd seek your opinions from you fella whose knowledge and discussions I really value ane respect. Someone told me to use Mobil 1's 5W-30 during the summers and 0W-20 during the winters here. How does that idea sound to you? If you had a car that's supposed to use 5W-20, which would you use? M1's 5W-30, 0W-20, or Amsoil's 5W-20? Thanks for your time and courtesy.