Oil Burning 2006 GMC Envoy XL Denali w/ 5.3 V8

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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.
 
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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!
 

Cygnus_

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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.
 
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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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2006 and 225,000 miles time to say good bye . 15W-40 in Wi. winters ?
You know, aside from the oil consumption, I'll respectfully disagree. One member of my fleet is a 2004 Yukon XL 4x4 with the 5.3L that has like 276K miles, and starts, runs and drives great. I recently changed the spark plugs at an approximately 100K mile interval and they looked great aside from being worn to like .065"-.070" or so. I have no problem trusting it through another northern Maine winter.

That engine had always been a mild oil consumer at maybe a quart or so at 1,500 miles, but I chalked that up to the thin 5w30 on cold starts and evaporation. I've recently started running Shell T6 4w40 diesel oil through it, after a Berryman's B12 Chemtool flush, specifically for the zinc and phosphorus, and that seem to have reduced the oil consumption.
 
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Stepping up the grade is never risky. Insufficient HT/HS is what will damage, not a higher one.

A consumption of 1 quart in 200-300 miles is virtually catastrophic consumption. Any oil will eventually passivate the catalytic converter at that rate. This is one of the least of your concerns.
 
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We bought my son's 2006 Escape about 9 years ago with about 95k miles. It burned about a quart every 500 miles. We went with thicker oil which did not help the oil burning. He moved about 200 miles away, and was not putting a lot of miles on it, so he just kept an eye one it. Last year, at 199k miles, after reading several reports of people doing a B12 Chemtool soak to free up the oil rings with success, I decided to try it. Long story short, it worked great, and now burns about 1/3rd of a quart in 2000 miles. Huge reduction in oil consumption and no apparent downside. He claims that it seems to have slightly more power now. Just a thought, and I realize a 4 cylinder with vertical pistons would likely have better success than a v engine where the B12 would soak only part of the piston, but might be worth a try if the valve cover doesn't turn out to be the problem.
 
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That engine had always been a mild oil consumer at maybe a quart or so at 1,500 miles, but I chalked that up to the thin 5w30 on cold starts and evaporation. I've recently started running Shell T6 4w40 diesel oil through it, after a Berryman's B12 Chemtool flush, specifically for the zinc and phosphorus, and that seem to have reduced the oil consumption.
What would zinc and phosphorus do for a flush?
 
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With that type of consumption the last thing I'd be worried about is the catalytic converter. A few hundred more ppm of ZDDP from the diesel oils isn't going to matter much. I'd run the T6 15W40 or even something in a 50 grade oil.

Years ago I had a neighbor with a Chevy van with a 250 I-6 that burnt oil at the rate the OP is using oil. Back in that day I was changing oil every 3K miles, early to mid 1980's. I drained the oil into a clean pan poured it into Clorox bottles and gave it to him to burn in his van.
 
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A lot of people on here like to use M1 0w40 in that engine, you could always try that or a 5w40. I have an 04 but only uses a qt between changes so it's not really an issue for me as it's getting changed out, it has the standard version 5.3 iron block w/ 118k miles.
 
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Pcv valve replacement may help.
I can't remember if 2006 uses the new style with just a small hole and n ball inside
My 2006 used oil with valvoline but not as much with other oils, leaks a bit at rear main seal
Clogged Pcv valves is a big reason for oil consumption on many vehicles
 
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You know, aside from the oil consumption, I'll respectfully disagree. One member of my fleet is a 2004 Yukon XL 4x4 with the 5.3L that has like 276K miles, and starts, runs and drives great. I recently changed the spark plugs at an approximately 100K mile interval and they looked great aside from being worn to like .065"-.070" or so. I have no problem trusting it through another northern Maine winter.

That engine had always been a mild oil consumer at maybe a quart or so at 1,500 miles, but I chalked that up to the thin 5w30 on cold starts and evaporation. I've recently started running Shell T6 4w40 diesel oil through it, after a Berryman's B12 Chemtool flush, specifically for the zinc and phosphorus, and that seem to have reduced the oil consumption.
What would zinc and phosphorus do for a flush?
I believe you're misreading it @kschachn... It seems like the "zinc and phosphorus" remark was related to Rotella T6 5W40 part of the comment (yes, I see he called it Shell T6 4W40, but mistakes happen.) And "Berryman's B12 Chemtool flush" portion of the comment isn't related to oil or additives commentary, but more of a sequential time frame of usage of all said products. Basically should read: used the B12 flush and switched to T6 right after specifically for zinc & phosphorus. Correct me if I'm wrong @NorthBranchArmory.
 
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