Which oil should I use...Mobile 1 Synthetic 5W30 or 10W30?

I live in Denver, CO (it's cold here) and have a 2004 5.3L Z71 with 63,000miles. Which oil is best for my appication?

Thanks for the help!

 

5w 30 is best until 100K miles and over. After that I'd use 10w 30 in summer and 5w 30 in winter.

 

Are you the first owner of the vehicle? Do you know if the oil change schedule was followed?

 

Hey guys wassup, Im new at this forum thing, and idk how to get around, idk if you guys can answer my question but i got an 02 silvy that has a rollpan, and i was thinking of putting the SS bumper or escalade bumper and for the caddy bumper, im getting sick of the rollpan, its cracking and becoming a pile of rust, plus safety wise, its non existing, i was wondering since thetahoe and escalade have the same chassis, would the caddy bumper fit the silverado?? I mean i dont know anyone with an escalade that i can kinda just take his bumper off for a fit you know, but i really like the idea, its deff unique, at least down here in fla. so any help would be greatly appreciated, thanks!

 

I am the second owner. I don't know if the owner followed the oil change schedule, but with the shape the I bought the truck in, I would bet he stayed up on all maintenance. The truck is in perfect shape.

 

5w30 if its a cold climate...10w30 is about the same though...kinda like picking fly **** out of the pepper

 

On my 91 (before I modified the hell out of it) I got slightly better gas mileage out of 5w 30 in the winter. Summer, yeah it doesn't matter too much. I used 10w 30 in the summer just for the added protection because of the heat and sitting in traffic on those hot days.

 

In all honesty, either weight is fine. They both cover a very broad temperature range. The 5w30 will give slightly better gas mileage, but might not even be noticable. If you are running hard in the summer or pulling heavy loads, then the higher weight is advisable. Mobile 1 full syn is great. It maintains a more steady viscosity throughout the temperature range. However, if you are on a budget the old traditional oils are fine too (not as good as full syn, but good) as long as you change it regularly. Above all else, clean oil and oil filter is just about more important than anything.

 

It also helps to use a little dishliquid in your oil about half way between oil changes. Remember, a clean engine is a happy engine!