I just bought a used 2001 4WD 4DR Blazer. It has no owners manual in it, and the .pdf version on mygmlink.com does not state the recommended oil viscosity for my blazer. It refers to an index that is not included in the file. My oil cap says 5W30, but I just wanted to check with someone who actually has the owners manual to make sure that is the year round recommendation. Better yet, if someone would scan and email the desired page from their owners manual, that would be great. If you reply to this question, please state what year Blazer owners manual you are referring to....thanks.

 

I'm pretty sure that all of the newer 4.3L v6s run 5w30 year round. If you are in a warm climate (ie not upstate NY like me - or anywhere with snow in the winters), you can safely run 10w30, but it is always best to run what is specified by the manufacturer. I'll take a run out to my Bravada at lunch to check my manual, if it's not raining - if it is, I'll get a look at it on my way home from work.

Straight from AllDataDIY.com for my '00 Bravada AWD:
Generally speaking, synthetic oils maintain their viscosity better at temperature extremes (both cold & hot) than conventional oils do. Personally, I only run Mobil 1 synthetic oil and don't change it until it's atleast 5000 miles old.

 

you're right. pretty much all the newer gm's reccomend 5w30. it'll say right on the oil fill cap.

 

5w30 is the correct viscosity.
I work part time in a service center, 5w30 is the recommended oil for all 4.3L V6 engines in the s-series trucks.

I use Dono oil and change it every 5,000 miles as well. Although I hit 5,000 miles every 8 weeks.