Quote:
Originally Posted by Reiver
I live in Az so the weather now is mid 80's and that's too cool for 20w/50 on my fresh 930-10 SC.
I use 10w/40 when it cools and use the 20w/50 when we are in the 90's-100 +.....I see very little dif in oil pressure with the change once warmed up...the diff is on start up.
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My daughter is going to school in AZ, so I understand people's relative perception of temperature. At the same time, people on the east coast and northern locations are probably chuckling at your description of cool weather (mid-80's), especially in their winters.
Being from a more temperate climate of SoCal, I suggest mid-80s as warm enough for 20-50 oil, but then our temp. swings are closer but not as wide as yours. Once warmed up, the engine really doesn't care what the ambient temperature is unless it's +90ºF.
However, in the desert, it can be "cold" in the winter months (what, 45?). If the daytime temps swing 60 degrees, I suppose 15-40 would be fine, but 20-50 would offer more protection depending on your driving conditions and max. ambient temps. The charts say typical low-high temps in AZ, 45-105ºF.
Sherwood