Oil weight change in different seasons

[84gmcsierra]

So what is this crate motor ? details may help with a better recommendation

350, 4 bolt main. Running 10w30 right now as I just got it back about a month ago.

 

[Japanese]

350, 4 bolt main. Running 10w30 right now as I just got it back about a month ago.

What brand 10W-30 do you run? Is it full synthetic? Is the Rotella 15W-40 full synthetic?
How many miles does the truck have?
You don't need to go to 20W-50, that's for sure.

I usually believe that diesel oils don't belong in gasoline engines. However, if you decide to run 15W-40 diesel oil because you drive a truck, live in hot state, and temps. don't drop below 32*F in your region - I would choose Valvoline or Mobil before Shell.

If your concern to run Shell Rotella is price driven then I would say don't go cheap.
Matter of fact I had a froend who was running Shell Rotella 10W-30 diesel conventional (bought cheap at Menard's) oil in his Chrysler Voyager and was changing it every 3,000 miles. He ended up with excessive oil burning engine due for major overhaul.
Once he gave me that same oil to try it in my Civic and I could tell the engine was not sounding and working as smooth as with the same grade gasoline oil. And that was in the summer. I was inpatient to change it asap.

 

[DanL13]

Indeed, it can get plenty cold in the mountains. Probably not cold enough to make a 15w unworkable, but the point remains— not all of AZ is hot desert. And deserts can get super cold at night and FAST after sundown.

Yeah no where in Arizona is dropping below freezing or below zero for days, weeks, or months on end like a lot of the rest of us deal with.

 

[hemitom]

If you find your mechanic trust worthy I would go with his suggestion for an oil change if you are not happy with the results try a 40 weight.

 

[FZ1]

I have an 84 GMC Sierra and just had another engine put in, and the mechanic said run 30 weight in it all the time. I usually do 40 weight, of 15w40 Rotella since it is a used engine. I live in Arizona so would it hurt to go to a 15w40 all the time, and go up to a 20w50 in the summer or just stay with one weight?

Try what the mech. told you run. You could go up, based on burning, etc. 20w-50 seems too thick. .02