I have a 2006 LBZ. Low Oil Light came on and it was down 1 Gal after 8,000 miles. I have approx 71000 on this truck and change the oil and filters on a regular basis. Checked the oil today after about 1,000 miles and it was a quart low. When the truck used 1 Gal I was using Mobil 1 5W40. Switched back to Rotella 15W40. I also run a FS-2500 Bypass Filter. It was a quart low on the Rotella when I checked it this morning. I have not found any leaks anywhere. Any ideas?

1qt per 1000 miles is GM's "Golden Rule" for oil usage.

Mine used some oil the few times I ran a 5-40 during the hottest part of the year.

1qt per 1000 miles is GM's "Golden Rule" for oil usage.

Mine used some oil the few times I ran a 5-40 during the hottest part of the year.

What concerns me is that this truck has never used oil

xTooltipElement

http://gsi.xw.gm.com/si/images/gmLogoFlat.gif Service Information
http://gsi.xw.gm.com/si/images/bhome.gif (http://gsi.xw.gm.com/si/home.do) http://gsi.xw.gm.com/si/images/bpublication.gif (http://gsi.xw.gm.com/si/publications.do) http://gsi.xw.gm.com/si/images/bnumsrchbutton.gif (http://gsi.xw.gm.com/si/numberSearchLink.do) http://gsi.xw.gm.com/si/images/bnews.gif (http://gsi.xw.gm.com/si/newBulletins.do) http://gsi.xw.gm.com/si/images/ymkbutton.gif (http://gsi.xw.gm.com/si/bulletinSearchLink.do) http://gsi.xw.gm.com/si/images/feedback.gif (http://gsi.xw.gm.com/si/feedback.do?laborOpDesc=Oil+Consumption+Diagnosis&docSyskey=1343441&feedbackType=STD&from=sm&laborOpCode=) http://gsi.xw.gm.com/si/images/bhelp.gif (http://gsi.xw.gm.com/si/mainHelp.do)



2006 GMC Truck GMC K Sierra - 4WD (http://gsi.xw.gm.com/si/publications.do) | Sierra, Silverado (VIN C/K) Service Manual (http://gsi.xw.gm.com/si/showPubSection.do) | Engine (http://gsi.xw.gm.com/si/showPubSubsection.do) | Engine Mechanical - 6.6L (http://gsi.xw.gm.com/si/showPubServiceInfoTypes.do) | Diagnostic Information and Procedures (http://gsi.xw.gm.com/si/showDocumentList.do) | Document ID: 1343441
Oil Consumption Diagnosis
The accepted rate of oil consumption, not due to leaks, is the use of 0.946 liter (1 qt) or less within 379 liters (100 gallons) of fuel used. This rate only applies to vehicles under warranty, maintained in accordance with the appropriate maintenance schedule, driven at legal speeds and within design intent of the vehicle.
Oil economy should not be tested until the vehicle has accumulated at least 8000 km (5000 mi) and the oil has been changed for the first time. During initial engine break-in periods before the first oil change, oil consumption may exceed 1.9 liters (2 qts) or more per 379 liters (100 gallons) of fuel used.
Checks
Causes
Preliminary
The causes of excessive oil consumption may include the following conditions:
• External oil leaks
Refer to Oil Leak Diagnosis (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm).
• Incorrect oil level or improper reading of the oil level indicator
With the vehicle on a level surface, run the engine for a few minutes, allow adequate drain down time (2-3 minutes) and check for the correct engine oil level.
• Improper oil viscosity
Refer to the vehicle owners manual and use the recommended SAE grade and viscosity for the prevailing temperatures.
• Continuous high speed driving and/or severe usage
• Crankcase ventilation system restrictions or malfunctioning components
• Oil residue in the charge air cooler system is normal with a closed PCV system
• Worn valve guides and/or valve stems
• Worn or improperly installed valve stem oil seals
• Piston rings broken, worn, not seated properly
Allow adequate time for the rings to seat.
Replace worn piston rings as necessary.
• Piston and rings improperly installed or improperly fit to the cylinder bore

© 2008 General Motors Corporation. All rights reserved.

xTooltipElement
http://gsi.xw.gm.com/si/images/gmLogoFlat.gif Service Information
http://gsi.xw.gm.com/si/images/bhome.gif (http://gsi.xw.gm.com/si/home.do) http://gsi.xw.gm.com/si/images/bpublication.gif (http://gsi.xw.gm.com/si/publications.do) http://gsi.xw.gm.com/si/images/bnumsrchbutton.gif (http://gsi.xw.gm.com/si/numberSearchLink.do) http://gsi.xw.gm.com/si/images/bnews.gif (http://gsi.xw.gm.com/si/newBulletins.do) http://gsi.xw.gm.com/si/images/ymkbutton.gif (http://gsi.xw.gm.com/si/bulletinSearchLink.do) http://gsi.xw.gm.com/si/images/feedback.gif (http://gsi.xw.gm.com/si/feedback.do?laborOpDesc=&docSyskey=1343445&feedbackType=STD&from=sm&laborOpCode=) http://gsi.xw.gm.com/si/images/bhelp.gif (http://gsi.xw.gm.com/si/mainHelp.do)



2006 GMC Truck GMC K Sierra - 4WD (http://gsi.xw.gm.com/si/publications.do) | Sierra, Silverado (VIN C/K) Service Manual (http://gsi.xw.gm.com/si/showPubSection.do) | Engine (http://gsi.xw.gm.com/si/showPubSubsection.do) | Engine Mechanical - 6.6L (http://gsi.xw.gm.com/si/showPubServiceInfoTypes.do) | Diagnostic Information and Procedures (http://gsi.xw.gm.com/si/showDocumentList.do) | Document ID: 1343445
Oil Leak Diagnosis
Step
Action
Yes
No
Important: You can repair most fluid leaks by first visually locating the leak, repairing or replacing the component, or by resealing the gasket surface. Once the leak is identified, determine the cause of the leak. Repair the cause of the leak as well as the leak itself.
1
<LI type=1>Operate the vehicle until it reaches normal operating temperature. <LI type=1>Park the vehicle on a level surface, over a large sheet of paper or other clean surface. <LI type=1>Wait 15 minutes.
Check for drippings.Are drippings present?
Go to Step 2 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S02)
System OK
2
Can you identify the type of fluid and the approximate location of the leak?
Go to Step 7 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S07)
Go to Step 3 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S03)
3
<LI type=1>Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
Check for leaks at the following locations: • Sealing surfaces
• Fittings
• Cracked or damaged components
Can you identify the type of fluid and the approximate location of the leak?
Go to Step 7 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S07)
Go to Step 4 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S04)
4
<LI type=1>Completely clean the entire engine and surrounding components. <LI type=1>Apply an aerosol-type powder (baby powder, foot powder, etc.) to the suspected area. <LI type=1>Operate the vehicle for several kilometers/miles at normal operating temperature and at varying speeds.
Identify the type of fluid, and the approximate location of the leak, from the discolorations in the powder surface.Can you identify the type of fluid and the approximate location of the leak?
Go to Step 7 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S07)
Go to Step 5 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S05)
5
Use J 28428-E (http://gsi.xw.gm.com/si/showTif.do?image=62292) in order to identify the type of fluid, and the approximate location of the leak. Refer to the manufacturer's instructions when using the tool.
Can you identify the type of fluid and the approximate location of the leak?
Go to Step 7 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S07)
Go to Step 6 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S06)
6
<LI type=1>Visually inspect the suspected area. Use a small mirror to assist in looking at hard to see areas.
Check for leaks at the following locations: • Sealing surfaces
• Fittings
• Cracked or damaged components
Can you identify the type of fluid and the approximate location of the leak?
Go to Step 7 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S07)
System OK
7
<LI type=1>Inspect the engine for mechanical damage and repair or replace as necessary. Special attention should be shown to the following areas: • Plugged or malfunctioning crankcase ventilation system. Refer to Crankcase Ventilation System Inspection/Diagnosis (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121510&refDoc=1343445&from=sm).
• Higher than recommended fluid levels
• Higher than recommended fluid pressures
• Plugged or malfunctioning fluid filters or pressure bypass valves
• Improperly tightened or damaged fasteners
• Cracked or porous components
• Improper sealants or gaskets where required
• Improper sealant or gasket installation
• Damaged or worn gaskets or seals
• Damaged or worn sealing surfaces
Inspect the engine for customer modifications.Is there mechanical damage, or customer modifications to the engine?
Go to Step 8 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S08)
System OK
8
Repair or replace all damaged or modified components.
Does the engine still leak oil?
Go to Step 1 (http://gsi.xw.gm.com/si/cellHandler.do?cellId=121509&refDoc=1343441&from=sm#S01)
System OK

© 2008 General Motors Corporation. All rights reserved.

try changing to like delo 15w 40 or even a thicker wieght oil. i use 15w 40 delo and i never had a problem like that with this oil i did when i was using amsoil.
.
but on the other hand i used 2 gals in like 5000 mile then my turbo blew. only have 99500 and some change but i now have a ATs 3000 turbo and i dont have that problem now. look on the out putside from the turbo to intercooler take the pipe off of the turbo and see if there more oil than normal.