Oil Burning 2006 GMC Envoy XL Denali w/ 5.3 V8

Joined
Aug 7, 2018
Messages
45
Location
WI
So, I will be asking a few questions here.

1) My mother has the vehicle specified in the title. It has 225K miles on it and uses quite a bit of oil, unfortunately, but runs fantastic otherwise. From what Ive heard from other mechanics, these engines are known for this in this generation. This is from worn valve guides from what I hear. I had the idea that running a thicker oil would slow the oil usage down some. It calls for 5w-30, but I stepped it up just about a month ago to Shell Rotella T6 15w-40. I understood from the resident diesel mechanic in my family that HDEO diesel oil can be run in a gas engine without issues. Now reading through some posts on this forum and others, that could do damage to the catalyst used on a gas engine if the HDEO doesn't have an S or "spark" rating because of high ZDDP and other additives in the oil. Is this something I need to be concerned about? So far, it doesn't seem to have slowed it down much. I am adding about a quart of oil every week or two which may correlate to 100-200 miles of driving or less.

2) Is stepping the viscosity of the oil up like this risky as far as engine wear or damage goes? There seem to be conflicting opinions on this from what I've read on here and other forums. I live in Wisconsin where temps are regularly 75-90 F in the summer and -20 - -30 F in the winter. Knowing that I would think I would want to change it to 5w-40 at least before the cold weather hits so the oil can be pumped better at those cold temps.

I may start running HDEO that also has an SN or better rating on it (such as Chevron Delo 400) in all of our vehicles as they all have 200K+ on them and want them to run as long as possible.
 
Joined
Nov 30, 2004
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2,539
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SD
As long as it has the gas spec (ie SN) also, it's fine to use. A quart of oil every 100-200 miles...yikes!
 

ArazelEternal

Thread starter
Joined
Aug 7, 2018
Messages
45
Location
WI
The oil usage issue is due to worn valve guides. The oil seeps down the valve guides into the combustion chamber and that is where it burns. A new vehicle is not in the cards right now, so I'm trying to keep it running as long as I can. We have always had high-mileage vehicles. We have never had a lot of money for anything like that so we tend to keep driving vehicles until the engine or trans fails, or the frame rusts out. And the 1 quart per hundred miles is an exaggeration, but it uses a lot.
 
Joined
Aug 11, 2011
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4,710
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N.C.
I have read that a few years of the 5.3 had PCV valve issues that would cause oil consumption problems. The PCV valves in certain model years were in the drivers side valve covers and not serviceable. The fix iirc was to replace the drivers side valve cover with a new redesigned cover with an updated PCV valve. IDK if this fix applies to your model but there are several YouTube videos on this problem.
 
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