Mystery Oil Loss - Where is the oil going? 2008 Yukon Denali

rdezs · Apr 7, 2025

Kind of sort of full bore.... But actually through a metered orifice on the models without the PCV valve. Not sure what year they drop the PCV valve, around 2004 or 2005?

That orifice is built into the driver side valve cover. if you have a lot of blow by it could potentially get plugged fairly easy. You can see the orifice if you pull the hose off and look straight down into the opening. You can clean it with a small drill bit. I wouldn't recommend enlarging it, will probably suck a bunch more oil into your intake

Fless · Apr 7, 2025

Best to do the valve cover TSB like @donjetman posted in #15.

My 2004 does NOT have a rattle PCV valve, it's integral to the DS valve cover.

steiny93 · Apr 14, 2025

Gildan said:
I drive less than 50 to 100 miles locally, go home in the evening and the oil is exactly full. The next morning I check the oil and a quart has vanished. There is no oil on the ground in the garage, and absolutely no sign of a leak anywhere. But, sitting over night, a quart of oil has vanished. This will happen every two days just like clockwork. Every two days. Sometimes a quart of oil will vanish in a 20 mile trip, no smoke, no leaks, no nothing).

per the above; means it isn't burning the quart as the oil loss happens without the engine running

at night after driving, full at dipstick
in the morning, not being driven at all, 1 quart low

How many quarts have you added on 1 oil change? IE, if this happens every 2 days have you added say 10 quarts since the last oil change?
If you wait 4 days do you lose 2 quarts?

Maybe do a video as to how you are checking the oil level. If it's using 1 qt to 100 miles; you'll see it.

Mystery Oil Loss - Where is the oil going? 2008 Yukon Denali

rdezs

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Fless

steiny93

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