Should i use 5w-20 oil living in the mountains?

i use 85 octane gas hereShould i use 5w-20 oil living in the mountains?
been driving over 40 yrs ive never used anything under 5w30 an dwhere i once live would get down 30 below an dit doesnt have much to do with anything about what fuel you using i wouldnt use it unless it stays below 30 or 40 below al lthe time sure that would help but what about times when its in the 80's not so great thenShould i use 5w-20 oil living in the mountains?
The owners manual will either say use only 5w-20 or have a chart based on expected temps. Go with what the manual says. My 05 dodge with the Hemi says 5w20 period so thats what I use. I believe Ford also has many engines that are supposed to only run 5w20 also.
The recommended oil viscosity depends on temperature, not altitude. Use what's recommended in your owners manual.
Still have the original oil cap? It tells you right there what is the recommended viscosity (aka weight) is.

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