Which oil for 2003 Silverado 6.0L?

[Yukon_2A_FTW]

New to the forum

I have a 2003 Chevy Silverado LL LQ9 6.0 with 203k miles. 4l80e AWD. Has kooks long tube headers/full exhaust. Truck runs great. No oil loss between services. Oil pan is very lightly wet but not dripping. Oil pressure is 35psi at warm idle with current Mobil 1 High Mileage 5w30. I live in Alaska where it gets -40F give or take in winter and 80F give or take in summer. Truck is daily driver and idles a bit in winter and summer occasionally does some short wot pulls. I've looked and looked and get tons of conflicting info on what oil I should use. Should i use the Mobil 1 High Mileage Full Synthetic 5w30 or change to something like Mobil 1 FS 0W-40 for cold factor and summer pulls? Gets oil changed late fall and early spring. I'm sure I am over thinking it lol.

Thanks

 

[fantastic]

Mobil 1 ESP 0w-30 or that Mobil 1 ESP 0w-40 would be good

 

[PontiacHO]

Whatever it’s had for 23 years has done the job. Carry on.

 

[CleanSump]

current Mobil 1 High Mileage 5w30

And Bob is your uncle. Unless you want to go to 0W-X for the -40F cranking. If you've had no problems with Winter starts, there's no need to change to a 0W-30/40 and if you're not consuming oil, no need for the -40 as a bandaid.
Maybe consider the current darling Valvoline Restore and Protect 5W-30 if you do have consumption to see if it's dirty rings that can be cleaned up.

 

[melk]

Nice engine. Mobil 1 ESP 0w30 is a great choice

 

[Kira]

A 2003 "Alaska truck" with 203k miles!
A picture or two sure would be appreciated.

 

[BrendanC]

Mobil 1 0w-40 would be my pick. i run HPL 5w-40 in my 6.0 in Texas. keep the oil changed and that 6.0 will go on forever. i have 247k miles and 12,000 engine hours. still runs like a top and drive it everywhere.

 

[SwampSurvivor]

I'd stick with whatever got it to 200k miles.

 

[BrendanC]

I'd stick with whatever got it to 200k miles.

a non AFM LS will make 200k miles with cooking oil in the sump. doesn’t mean there aren’t better options for the same cost.

 

[fantastic]

A 2003 "Alaska truck" with 203k miles!
A picture or two sure would be appreciated.

Maybe not a good idea.

 

[Snagglefoot]

I have a 2008 6.0 closing in on 300,000 miles. Runs well. An oil analysis reveals some cam bearing wear which is normal. I went to a 5W40 for the summer but for cold weather in Alaska I would use a 0W40. What I actually do is run 0W30 in the winter and 5W40 in the summer.

 

[BrendanC]

I have a 2008 6.0 closing in on 300,000 miles. Runs well. An oil analysis reveals some cam bearing wear which is normal. I went to a 5W40 for the summer but for cold weather in Alaska I would use a 0W40. What I actually do is run 0W30 in the winter and 5W40 in the summer.

aslong as you never lay eyes on the cam bearings, they’ll run forever. it’s like the magic smoke in electronics.

 

[JavierH19]

What's your hot oil pressure during the winter. And I imagine it has the transmission oil cooler that goes to the radiator. What is the highest temp of that during the cold. Engines can run cold enough up there that even if you bump down a grade the oil might as well be thick enough to still be up a grade in warm weather in some cases. If you can locate 0w-30 for not much more I'd use it. But if you use a block heater in the winter 5w-30 will continue to be fine.