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Discussion Starter #1
Truck currently has 196k on it and within the last couple months I have been having some oil consumption/missing issues. I have absolutely no leaks, trust me it's a major pet peeve. I always change oil at ~3,000 miles and usually check oil level before long trips. I also have no smoke at all, even at high RPM's.

I use Trop Arctic 5W-30 as I have seen major improvements in carbon buildup reduction using this product.

The last two oil changes have been weird tho...

As I said I check it regularly, and have noticed I am missing quite a large amount of oil lately. The last oil change I checked it at approximately 1,500 miles and I was a quart low (not touching the dip stick). I refilled and kept driving until my next oil change (194k). I changed the oil (6 quarts, I know) and drove to town. I drove back home and checked again to be sure. I was a quart low, wtf? I put in another quart to make 7 quarts and it was at F again (level surface, brand new garage).

I am now up to 196,500, and checked again to find I was a quart and a quarter low.

I have a slight amount of milky oil coming from the breather, but nothing that would explain the amount of oil I am loosing. I don't have missing coolant and it is a perfect red GM coolant color. The exhaust is black from carbon, but from talking to James I need to replace my O2 sensors (ordered), and do something about my upstream CAT as it is probably clogged.

I have read that the PCV vent valve can clog and cause the milky oil, but that still does not explain the massive amounts of oil. I parked in a garage for 2 weeks and did not find any puddles even after daily town driving of 30-40 a day, as I live in the outskirts of town.

Any help would be appreciated in advance. BTW, I have read the threads on head gaskets and I am not experiencing the symptoms (heater issues, coolant in oil, oil in coolant, etc)

I am considering switching to 10W-30 in the winter, and 15W-40 in the summer since it is a very high mileage vehicle.
 

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Discussion Starter #3

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There is no valve but a metered orifice. It is located on the right side hose at the valve cover. That is the hose going to the resonator box. Here is a pic of my valve cover. It is the smaller hole.
 

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Discussion Starter #5
To be sure...
The one in green, being the one with that connects with a hose to the intake, is the one containing the metered orifice? Or is it the one in blue?
ValveCover002.jpg
I am assuming the one in blue is the vent to atmosphere, correct? The one in green is definitely the one that has a hose to the intake for recirculation.
 

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Discussion Starter #10
Besides the PCV, what else should I look for on this oil usage? I really doubt that head gaskets are causing this, I am just out of things to try.
 

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Are you getting any kind of smoke during such activities as when you first start it up, or during deceleration or acceleration?
 

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As BigR said, there isn't a pcv valve in these engines. There is an orifice (2.5mm/0.098in) that controls the flow of vapor. The two hoses at the rear of the camshaft (valve) cover are for the PCV system. The hose that connects to the resonator is the "fresh air" (inlet) hose and the hose that connects to the intake is the "dirty air" connection. If the PCV orifice gets plugged, the vapors will back flow out of the fresh air hose and into the resonator. If that outlet is plugged also, IMO, it could cause some oil loss if it creates a higher than normal pressure inside a high mileage engine that forces oil past the rings. It could be a small, but steady amount, that wouldn't necessarily be visible in the exhaust. It could also eventually cause problems with the converter(s).

A #40 drill bit is 0.098", A 3/32 drill bit is 0.0935. If you are very well equipped, a 2.45mm bit is 0.0964. :)
 

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Discussion Starter #13
Are you getting any kind of smoke during such activities as when you first start it up, or during deceleration or acceleration?
I do not get any smoke at all. As listed in the OP I had my girlfriend follow me when driving hard. She couldn't see it or smell it.

As BigR said, there isn't a pcv valve in these engines. There is an orifice (2.5mm/0.098in) that controls the flow of vapor. The two hoses at the rear of the camshaft (valve) cover are for the PCV system. The hose that connects to the resonator is the "fresh air" (inlet) hose and the hose that connects to the intake is the "dirty air" connection. If the PCV orifice gets plugged, the vapors will back flow out of the fresh air hose and into the resonator. If that outlet is plugged also, IMO, it could cause some oil loss if it creates a higher than normal pressure inside a high mileage engine that forces oil past the rings. It could be a small, but steady amount, that wouldn't necessarily be visible in the exhaust. It could also eventually cause problems with the converter(s).

A #40 drill bit is 0.098", A 3/32 drill bit is 0.0935. If you are very well equipped, a 2.45mm bit is 0.0964. :)
Sounds like this could be reasonable. I have a custom intake and I will check it hopefully tonight to see if there is any pooling in the intake tubes with oil. According to what you said, even if there isn't any in there I could still be burning it through blow-by on my oil rings.
 

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If you have a custom intake, check to make sure that the PCV intake "fresh air" hose, that used to be connected to the resonator, is installed properly and functioning.
 

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Good info guys!

Been looking through my archives to find the pics of one member who ended up removing his valve cover. He found some debris that looked like an O-ring that was clogging the passenger side rear vent. Same symptoms as the OP is having.
 

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Discussion Starter #16
If you have a custom intake, check to make sure that the PCV intake "fresh air" hose, that used to be connected to the resonator, is installed properly and functioning.
Ill check that tonight!

Good info guys!

Been looking through my archives to find the pics of one member who ended up removing his valve cover. He found some debris that looked like an O-ring that was clogging the passenger side rear vent. Same symptoms as the OP is having.
Do I need to pull the valve cover to check that vent James?

Thanks everyone for contributing so far!
 

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Ill check that tonight!



Do I need to pull the valve cover to check that vent James?

Thanks everyone for contributing so far!

I would first try to clean it with a pipe cleaner or as mentioned a drill bit.
Clean out any debris and see if your problem is resolved.
 

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Discussion Starter #20
I don't know how you guys survive! I have a fit if I have to put long pants on.
It feels nicer than usual today actually. I feel like I might actually be able to work on this today haha. I've got classes until 2PM today, so after that I got to make a call to a wheelchair company and then I should be able to go outside and work on the pickup.
 
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