Choosing the appropriate oil

[Mettalikatt]

1. 2004 GMC Sierra with a 5.3L Gas engine @135k miles
2. Don't have an owner's manual unfortunately, but recommended viscosity is 5/30
3. Central Oklahoma
4. I tend to drive the truck moderate to hard
5. I drive both city and highway about 50 miles everyday, maybe 10-15 of these are highway miles.
6. No currently known mechanical problems

I'm currently running Royal Purple 5w30 in the truck, it's the first oil I put in it when i purchased the truck 7k miles ago. Now that it's time for another oil change I'd like to figure out what I really need to do to prolong the life of my engine. For the past 7k miles i haven't burnt or leaked any oil running RP. I'd like to stick with a synthetic oil because of the larger change intervals. Should I still run 5w30 on an engine with 135k miles? and if so what oils are recommended by the gurus? Castrol Syntec, Mobil 1, Royal Purple, Quaker State?

TLDR: Truck has 135k miles, no leaks, running RP 5w30 want to know if alternatives are better.

 

[DinoLover]

To prolong the life of your engine my guess is that changing how you drive the truck from "moderate to hard" to "easy to moderate" would have a bigger impact than which of those oils you choose!

 

[fxrider]

Pennzoil Platinum 5W30 would be a great Choice. So would Mobil 1 Extended Performance 5w30 .

 

[Garak]

Originally Posted By: Mettalikatt
Should I still run 5w30 on an engine with 135k miles? and if so what oils are recommended by the gurus? Castrol Syntec, Mobil 1, Royal Purple, Quaker State?


Any conventional would do the trick. However, you want to extend and use synthetics. Since it's not consuming or leaking 5w30, there's simply no reason to change what you're doing now. If you like RP, keep on with it. If you want to vote with your wallet, any of the others you listed would do just fine, too.