When I was a tech at the dealer we had a ton of issues like this with the northstar engine due to carbon build up at the rings. At that time it was mostly older people who were buying Cadillacs and I'm not picking on them but most older people don't drive their stuff very hard, ya know it only idles to the grocery store once a week. They simply never blew out the carbon so we would have to try to clean the carbon with top engine cleaner. Most of the time we were successful but I would always advise the customer to hop on the freeway and floor it from time to time. I would try a top engine soak overnight and drive the hell out of it for a few days. If that doesn't get it to stop eating oil I would pull the heads and look at the cylinder walls you might have a issue with the way it way it was honed at the factory.
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There are many technical service bulletins out on oil consumption on active fuel management engines, 2007 up.

Engine Oil Consumption on Aluminum
Block/Iron Block Engines with Active Fuel Management (AFM) (Install AFM Oil Deflector and Clean Carbon from Cylinder and/or Install Updated Valve Cover) (Jan 3 2013)

Subject: Engine Oil Consumption on Aluminum Block/Iron Block Engines with
Active Fuel Management (AFM) (Install AFM Oil Deflector and Clean
Carbon from Cylinder and/or Install Updated Valve Cover)

Models: 2007-2011
Cadillac Escalade Models
2007-2011 Chevrolet Avalanche, Silverado 1500, Suburban, Tahoe
2010-2011 Chevrolet Camaro
2007-2011 GMC Sierra 1500, Sierra Denali, Yukon Models
2008-2009 Pontiac G8 GT

Built Prior to February 1, 2011 (Updated Valve Cover) and October 2010 (AFM Shield)
Equipped with Any of the Following Engines:
– Aluminum Block V8 Engine with Active Fuel Management (AFM) (RPOs L94, LZ1,
L99, LC9, LH6, L76, LFA, L92)
– Iron Block V8 Engine with Active Fuel Management (AFM) (RPOs LMG, LY5)
– Hybrid Engine (RPO LFA – Only Applies to Hybrid Models Built July 7, 2009 February
1, 2011 – Prior Builds Not Cast For AFM Valve)

Attention: This bulletin does not apply to the Buick Rainier, Chevrolet TrailBlazer and
GMC Envoy equipped with LH6 due to a different design oil pan and AFM
pressure relief valve.

This bulletin is being revised to update the Warranty Information. Please discard Corporate
Bulletin Number 10-06-01-008F
(Section 06 – Engine/Propulsion System).

#10-06-01-008I: Engine Oil Consumption on Aluminum Block/Iron Block Engines with Active Fuel Management (AFM) (Install AFM Oil Deflector and Clean Carbon from Cylinder and/or Install Updated Valve Cover) - (Feb 19, 2013)
Subject: Engine Oil Consumption on Aluminum Block/Iron Block Engines with Active Fuel Management (AFM) (Install AFM Oil Deflector and Clean Carbon from Cylinder and/or Install Updated Valve Cover)

Models: 2007-2011 Cadillac Escalade Models
2007-2011 Chevrolet Avalanche, Silverado 1500, Suburban, Tahoe
2010-2011 Chevrolet Camaro
2007-2011 GMC Sierra 1500, Sierra Denali, Yukon Models
2008-2009 Pontiac G8 GT
Built Prior to February 1, 2011 (Updated Valve Cover) and October 2010 (AFM Shield)
Equipped with Any of the Following Engines:
– Aluminum Block V8 Engine with Active Fuel Management (AFM) (RPOs L94, LZ1, L99, LC9, LH6, L76, L92, LFA (Hybrid))
– Iron Block V8 Engine with Active Fuel Management (AFM) (RPOs LMG, LY5)
Attention: This bulletin does not apply to the Buick Rainier, Chevrolet TrailBlazer and GMC Envoy equipped with LH6 due to a different design oil pan and AFM pressure relief valve.
This bulletin is being revised to update the Warranty Information. Please discard Corporate Bulletin Number 10-06-01-008H (Section 06 – Engine/Propulsion System).

Condition
Some customers may comment about engine oil consumption of vehicles with higher mileage (approximately 48,000 to 64,000 km (30,000 to 40,000 mi) and a service engine soon light being on and/or rough running engine. Verify that the PCV system is functioning properly. If the customer understands that some oil consumption is normal and still feels the consumption level is excessive, more than 1 quart per 2000 to 3000 miles of driving, perform the service indicated in this bulletin. It is no longer necessary to have the customer return multiple times to have the usage verified.

Cause
This condition may be caused by two conditions. Oil pulled through the PCV system or oil spray that is discharged from the AFM pressure relief valve within the crankcase. Under most driving conditions and drive cycles, the discharged oil does not cause a problem. Under certain drive cycles (extended high engine speed operation), in combination with parts at the high end of their tolerance specification, the oil spray quantity may be more than usual, resulting in excessive deposit formation in the piston ring grooves, causing increased oil consumption and cracked or fouled spark plugs (#1 and/or #7). Refer to the latest version of Corporate Bulletin Number 12-06-01-001.

Correction
Aluminum or Cast Iron Block - Oil in Intake Manifold - Install Updated Valve Cover on All Models Built Prior to February 1, 2011
Note: If vehicle is built after this breakpoint, it should already be equipped with this updated valve cover.

Object ID: 2740641Click here for detailed picture of the image.
1) Old Design

2) New Design

PCV pullover or an overactive lifter can cause oil to be pulled through the PCV system even at low vehicle mileage. A correctly functioning PCV system will only leave a film of oil in the intake manifold. Inspect the intake manifold to see if there is any oil puddling in the bottom. If there is you will need to replace the left valve cover. Two new left rocker arm covers have been released for trucks and vans. Technicians should replace the left rocker arm cover with GM P/N 12570427 for 2007-2008 or GM P/N 12642655 for 2009-2011. Refer to the Parts Information below for the Camaro. This rocker arm cover has a relocated PCV drain hole that prevents oil from entering the intake manifold. Refer to Valve Rocker Arm Cover Replacement - Left Side in SI.

Note: These rocker covers are for specific years. The PCV orifice is different for each. The correct cover must be used or an SES light may set.

Aluminum Block - Oil Getting Past Piston Rings - Free Up Piston Rings and Install AFM Shield on All Non-Hybrid Models Built Prior to October 1, 2010 or all Hybrid Models Built July 7, 2009 - October 1, 2010
Note: If vehicle is built outside of this breakpoint, it should already be equipped with this AFM shield or the pan does not have an AFM valve (LFA before July 7, 2009).

To correct this condition, install an AFM shield, perform the piston cleaning procedure as described in this document and install a new oil pan gasket per the procedure outlined in this document. Monitor oil consumption after this repair to ensure oil consumption has improved to acceptable levels.

If this repair does not correct the condition, it may be necessary to replace all of the piston assemblies (piston and rings) with new parts. Refer to SI for repair procedure.

Important: It is critical in this cleaning process that the engine/fuel injector cleaner remain in the cylinders for a minimum of 2.5 hours to fully clean the components. The cleaner solution must be removed before a maximum of three hours.

Remove the spark plugs and ensure that none of the pistons are at top dead center (TDC).
Clean the pistons by putting 118-147 ml (4-5 oz) of Upper Engine and Fuel Injector Cleaner, GM P/N 88861803 (in Canada, use 88861804), in each cylinder. Allow the material to soak for at least 2.5-3.0 hours, but no more than three hours and then remove the cleaner. A suggested method of removing the cleaner is cranking the engine over. Make sure to unplug the ignition coils and fuel injector before cranking the engine over. Also make sure that the painted surfaces are covered so no damage is done.
Remove the oil pan. Refer to Oil Pan Replacement in SI.
Object ID: 2474205Click here for detailed picture of the image.
Remove the AFM valve (1).
Object ID: 2474207Click here for detailed picture of the image.
Install the new shield (1), GM P/N 12639759, and tighten the AFM valve to the oil pan to 28 Y (20 lb ft).
Important: Ensure that the engine cleaner is thoroughly removed before reinstalling the spark plugs. Failure to do so may result in a hydro-lock condition.
Reinstall the spark plugs. Replace the spark plugs if necessary due to full of carbon. Refer to the parts catalog.
Reinstall the oil pan. Refer to the Oil Pan Installation procedure in SI. Replace the oil pan gasket if necessary. Refer to the parts catalog. Replace the engine oil.
Re-evaluate the oil consumption. Document on the repair order. If the oil consumption is still greater than 0.946 L (1 qt) in 3,200 km (2000 mi), replacement of the pistons and rings will be required.
Important: Some minor scratches may be noticed on the cylinder walls during piston and ring replacement. If the scratch cannot be felt when running your finger nail over it, the scratch is considered normal wear and the block or engine should not be replaced.

Note: It is not necessary to hone or deglaze the cylinder walls. Honing may induce unnecessary cylinder wall and / or piston ring damage if it is done incorrectly and/or not cleaned thoroughly. Cylinder walls should cleaned thoroughly with brake cleaner before installation of the new pistons and rings. Numerous engines replaced for oil consumption have been inspected. The cross hatch has been consistently good and is in specification. As a result, is should not be necessary to measure the cylinders if they pass the visual inspection.

Note: After the piston/ring replacement it will take 2000-3000 mi. for the new rings to seat. Adequate break time is necessary prior to rechecking the oil consumption level.

Note: Do not overlook the valve seals at higher mileage. Look in the head ports for evidence of excessive amounts of oil getting past the seals.

Note: It is recommended to install an AFM shield any time that the oil pan is removed for any reason and an AFM shield is not found.

Cast-Iron Block - Oil Getting Past Piston Rings - Free Up Piston Rings on All Models Built Prior to October 1, 2010
Remove the spark plugs and ensure that none of the pistons are at top dead center (TDC).
Clean the pistons by putting 118-147 ml (4-5 oz) of Upper Engine and Fuel Injector Cleaner, GM P/N 88861803 (in Canada, use 88861804), in each cylinder. Allow the material to soak for at least 2.5-3.0 hours, but no more than three hours and then remove the cleaner. A suggested method of removing the cleaner is cranking the engine over. Make sure to unplug the ignition coils and fuel injector before cranking the engine over. Also make sure that the painted surfaces are covered so no damage is done.
Important: Ensure that the engine cleaner is thoroughly removed before reinstalling the spark plugs. Failure to do so may result in a hydro-lock condition.
Reinstall the spark plugs. Replace the spark plugs if necessary due to full of carbon. Refer to the parts catalog.
Re-evaluate the oil consumption. Document on the repair order. If the oil consumption is still greater than 0.946 L (1 qt) in 3,200 km (2000 mi), replacement of the pistons and rings will be required.
Note: It is not necessary to install the shield when doing the piston cleaning on a cast iron block engine since the cast iron block engine uses a different oil pump than an aluminum block engine, which results in a higher engine speed before the AFM pressure relief valve opens (cast iron block engines are less prone to the AFM oil spray condition described earlier). If you find it necessary to replace the pistons and/or remove the oil pan for any other reason, only then should you add the shield.
Object ID: 2596639Click here for detailed picture of the image.
__________________
2009 PSM 6.0
Corsa Cat-back, Volant intake w/AFE filter, BMR sway bars, BMR strut tower brace, 93 octane tune/DOD disabled, rotofab engine covers, MGP caliper covers, ebay catch can, hsrk, 35% tint, E&G grille inserts Important: Some minor scratches may be noticed on the cylinder walls during piston and ring replacement. If the scratch cannot be felt when running your finger nail over it, the scratch is considered normal wear and the block or engine should not be replaced.

Note: It is not necessary to hone or deglaze the cylinder walls. Honing may induce unnecessary cylinder wall and / or piston ring damage if it is done incorrectly and/or not cleaned thoroughly. Cylinder walls should cleaned thoroughly with brake cleaner before installation of the new pistons and rings. Numerous engines replaced for oil consumption have been inspected. The cross hatch has been consistently good and is in specification. As a result, is should not be necessary to measure the cylinders if they pass the visual inspection.

I have a 2004 Sierra Z71 with the 5.3. It consumes 1.5 - 2 Qt. of oil every 1500 miles, and I have to clean or replace spark plugs every few months due to fouling out. all plugs appear to have the same amount of buildup. Things I have done 1. replaced heads, all new seals and everything. 2. inspected all cylinders, no signs of wear or scoring, above normal. 3.compression tested all cylinders. all tested within 5 psi of each other and well within GM specs. and last 4. replaced left valve cover with the PCV baffles (i just did #4 today) if #4 doesn't sole the oil consumption issue, can anyone give me some kind of idea where to go from here. if not I am going to drive the thing off a cliff and replace the truck with a ford, and that would suck because I have had GM'* for all my life.

an 04 wouldnt have afm issues like the newer ones, and i dont believe there are any fluids in the intake on a ls engine. so you have oil in the cylinder and the compression is good so its a head issue like valve guides. there was an issue with cracked heads(do a search on castec), but normally that results in coolant in the oil like headgasket issues, so take a look at your coolant for signs of mixing

As mentioned the 04 doesn't have the afm setup and very rarely have consumption issues. Does it have a lot of miles, possibly worn oil rings. Worn oil rings wont show up for a compression test. Pcv valve operating correctly?

When i had the head off, ! did not see any indication the the rings were bad. I replaced the valve cover that has the PVC baffle setup. still monitoring to see if oil consumption decreases or stops. I have 150,000 miles on the truck.

Under some conditions regardless of piston ring wear and valve stem clearance/wear/seals issues you can have plugged crankcase ventilation. The crankcase can then become pressurized and oil may be forced under this pressure down the valve guides and past the piston rings and burned excessively. I have seen certain Volvo 240s with low miles do.(20k miles) Seems like it was 81-85 models. Any way a cheap fix to stop the oil burning..