Do I use 5w-30 or 10w-30?

[Black02Silverado]

sierra pretty much nailed it. The first number is the oils ability to flow when cold before the engine is up to operating temp. Considering where you live I would just go with the ASL 5w-30 and roll. Now if you can afford AMSOIL's Signature series 0w-30 that would be a good choice but in my experiences with oil analysis, I got the best results running AMSOIL's HDD 5w-30 diesel oil. Yes a diesel oil in a gas engine. It provided great results over the others in my Silverado.

 

[DarrenWS6]

Use what the oil cap says or what the owners manuel says for your climate.

Couldn't have said it any better.

 

[sand man]

OK So what about me? in summer it hits 50-55 celsuse(130 f) easy

i use 10w30 now

 

[dietz4ibanez]

I'll agree. 5W30 changed regularly won't hurt a thing. I just haven't seen it as recommended. Last 5.7 I owned was in my 97 Silverado. I actually ran 20W50 in all of my 5.7s. Never had any issues but we live in a very warm area.

Both the Black truck and Sierra recommended 5w-30 but when I got into high miles I switched to using 10w-30/40

 

[Black02Silverado]

I'll agree. 5W30 changed regularly won't hurt a thing. I just haven't seen it as recommended. Last 5.7 I owned was in my 97 Silverado. I actually ran 20W50 in all of my 5.7s. Never had any issues but we live in a very warm area.

Both the Black truck and Sierra recommended 5w-30 but when I got into high miles I switched to using 10w-30/40

Where do I find this mysterious 10w-30/40?

 

[merlin5577]

5W-30 is factory recommendation. In my 97' i'm running 5W-40. Just makes buying oil easier.