@badbearing and @acemaster IF you can plug in everywhere you can get by with 5W30, and synthetic is best. However, I have been in many places where I could not plug in and my 0W30 came in handy.
Mobil1 5W30 has a pour point of -47Celsius (-53F), their 0W40 has a pour point of -54C, (-65F), while a regular mineral 5W30 from Exxon has a pour point of -36Celsius (-32F). Big difference. Other oils show a similar or somewhat smaller difference. All vehicles used by the Alyeska Pipeline have standardized on Mobil1 because of its wide range of application.
Using 0W20 is not recommended, except in the latest Toyota cars. The “0” part will let you start in very cold temperatures, but the “20” is the hot viscosity, and in a 2005 Toyota you will likely have oil consumption or small leaks. This stuff, although good oil, is too thin in older cars. So, 0W20 IS NOT what you need, it’s 0W30 synthetic. The 0W20 Synthetic is now recommended for 2012 and 2013 models, since the y have oil activated valve gear, better oil control rings and tighter sealed engines…
My son has a 2004 Mazda3 with 200,000 miles on (no oil consumption to speak of) it and it has used 0W30 synthetic since new, although Ford and Mazda specified 5W20, which was not good for hot weather and high loads.