4.3 with 160,000 mi.

First let say this is a great site with people with a wealth on information. My S-10 has about 160,000 miles on it. I ve been using Mobile 1 5w30 since I bought and it still runs like a day bought it. I change the oil every 3000-5000 miles. It uses about 1/2 to 3/4 quart of oil between changes. Should I stay with the 5w30 or switch to a heaver oil like 10w30 ? Oh it is a 1997 4.3
Thanks RML  

Personally I would use 10w30 Mobile one. I used it in my 89 burb for 19 years now. 10w30 Mobile 1 still has a pour point of around 55 below (unlike even 5w30 conventional oil which would be jelly)  

What would the advantage in switching to the 10w30 over the 5w30 ?  

Heavy bodied oil. THere has been some wear in engine and this will thicken oil film some and float bearing a bit better. In old days, lighter weight oils were used to get them to flow better in colder temp SYN oil is more stable over a wider range of temperatures and does not need to be a really light weight to flow in cold weather. I put about 190K miles on mine with 10w30. For want it is worth, the only 5w anything I use in cars hear is that I use 5w20 in winter and 10w30 in summer in my daughters Saturn. I found it started and ran better with 5w20 vs 5w30 in cold weather and used a bit less gas too.