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2017 GMC Denali  6.2 , after my truck sits for a few days and i start up i notice a small puff of blue smoke coming from tail pipe.

My experience from other vehicles is that is usually an indication of oil seeping past valve seats. I have noticed that on other vehicles before ,but usually high mileage vehicles my truck only has 14K miles. 

Has anyone else noticed this or have and suggestions if that is normal for new engines or should I be concerned ?

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Perfectly normal for DI engine. They all do. 

 

Makes me wonder how we will diagnose valve stem seal issues now?

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I don't notice smoke emitting from my 2017 Sierra, BUT my work vehicle, a 2009 Acadia 3.6 DI will puff a small amount of black smoke upon cold startup. It has done it since new.

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mine is blue as in oil not black . What is DI ? direct injection ? 

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yes

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My 2014 Sierra would do the same on some days, not every start up. 

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I still have a 2010 denali pickup  with the 6.2 140,000 miles not blue smoke on start up . But on cold mornings it has a knock in engine at first start up which i think is valves ? maybe . Has been at dealer for problem and they did a decarbonization  of the engine and it didnt make any difference . Doesn't use any oil and runs great . Once it warms up about 20 secs knocking/clatter goes away . Dealer said GM said that is normal . 

Does anyone else have the same issue?

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2017 GMC Denali  6.2 , after my truck sits for a few days and i start up i notice a small puff of blue smoke coming from tail pipe.
My experience from other vehicles is that is usually an indication of oil seeping past valve seats. I have noticed that on other vehicles before ,but usually high mileage vehicles my truck only has 14K miles. 
Has anyone else noticed this or have and suggestions if that is normal for new engines or should I be concerned ?
Do you happen to park nose up, nose down, or cantered left or right when this happens?

Sent from my SAMSUNG-SM-G900A using Tapatalk

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4 hours ago, Tbounds said:

mine is blue as in oil not black . What is DI ? direct injection ? 

Correct, Direct Injection. They all smoke from time to time on startup, especially a cold start (not implying arctic conditions, just a block at room temp). Should be darker in color, very “sooty”, and since it’s derived from fuel not oil, it shouldn’t smell like burned oil. 

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14 minutes ago, Tbounds said:

I still have a 2010 denali pickup  with the 6.2 140,000 miles not blue smoke on start up . But on cold mornings it has a knock in engine at first start up which i think is valves ? maybe . Has been at dealer for problem and they did a decarbonization  of the engine and it didnt make any difference . Doesn't use any oil and runs great . Once it warms up about 20 secs knocking/clatter goes away . Dealer said GM said that is normal . 

Does anyone else have the same issue?

This is likely piston slap, and LS based engines are quite prone to it. If it’s excessively loud or doesn’t disappear with temp, then it could be an issue. 

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My 99 with a 5.3 sounded like a diesel on start up some days. Supposedly carbon build up above the top ring on the pistons. 

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I have a 2017 Sierra and I only use the 93 Octane and have read if you use lower gas your engine will get a knock. I have no issues and get great gas mileage. Hope this help. 

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