I dont know if this helps you, but I have a 05 silverado z71 and im using Royal Purple for my 5.3l vortec.

 

Mobile 1 5w30 synthetic.

 

valvolaine max life.

 

I use Mobil 1. I've ran it in everything from my 7 sec (1/8th) CRX Racecar to my wife's Lancer. Very good oil, never had any issues with changes in viscosity or pressure. If it is approved by Honda, it's obviously good, because they have one of the highest oil standards amongst car manufacturers.

 

I use Castrol High Mileage 10w30 in my car and both trucks. Seems to work well and it's nice being standardized in oil weight amongst all the vehicles. I think they all call for 5w30, but with the heat down here, I figure 10w30 works just as well if not better.

 

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1900434

 

Mobile 1 5w30 synthetic.

Times two!

 

Bought my 98 Suburban 3 years ago-195,000 miles-and switched it right away to Mobil 1 5W30-recently I switched it to 10w30 because I figured the slightly higher weight might be better for a high mile vehicle. No problems with it-great hy mpg for a huge vehicle.
I read somewhere that 10w30 starts with thicker base oil(probably longer chain molecules??) , and it needs fewer viscosity modifying molecules to pour like a 30 weight (at whatever temp it is measured at)- and will have relatively more pure "lubricating molecules." This sounded plausible , but that doesn't mean it is so.
I live in New Orleans-hot climate-so the oil is never as thick as it is in colder climates.

 

I run 10w-30 Castrol GTX with Lucas Oil Stabilizer.

 

Bigblue....good info thank you

 

Kendall GT-1 full synthetic with liquid titanium 5w30 in the truck and 10w30 in the GTP
i use it mainly because i get it for less than 2 bucks a quart at my work

 

I use either Mobil Clean 5000 or Castrol GTX 10w30. Both are great. Mobil Clean 5000 is good for 5000, but I change every 3k anyway, so I know it won't break down.
95 GMC Sierra 1500, 305 tbi

 

Good ol' Exxon Super flow in every car or truck i have ever owned.

 

Amsoil 0w30 with bypass system. in the o4 Tahoe, Amsoil 5w30 in 93 suburban 144k, XL 5w30 7500 k oil in 99 Astro 150k and counting.

 

I use Mobil - 1 synth. 5W - 30.

 

Mobil1 5-30

 

Quaker State 5-30 in a 02 5.3l

 

Mobile 1 5w30 synthetic.

X2. There's a poll on this topic in the polling place forum. Check it out at the link below.
http://www.gmtruckclub.com/forum/showthread.php?20345-What-oil-do-you-use

 

Mobil1 10W-30 since new

 

I use Amsoil 0w-30 and a Amsoil EA oil filter & change both out at 1 year or 35,000 miles which ever comes first.

 

Have been using Mobile 1 5-30 but recently bought a pail of Boss 5-30 supposedly every bit as good as Mobile.
I know a number of guys that have recently switch to Royal Purple and are now swearing by it as being the best.
My son just used my Boss oil in his Mercedes and traveled approximately 800 miles none stop and said every thing seemed to be fine.

Blessings,

 

I've been using royal purple 5-30w/10-30w (depending on summer/winter) since 60,000 miles. No problems so far!

 

I've been using mobil 1 5w-30 synthetic for awhile, but when I pick up a newer truck I'll be switching to royal purple since my friend can get it for cheap.

 

10/30 mobile 1. used it in every rig ive had

 

Valvoline 10w30, every 3 oil changes I put in a quart of Lucas oil stuff.