2020 GMC Sierra 6.8L Gasoline engine eats a lot of oil!!

[MachWun]

I have a 2020 Sierra 2500HD Denali with the Gasoline engine.  I did not have a problem or wasn't aware of one, until about a year ago.  Low oil light came about for the first time.  It took almost 3 quarts to get it into the cross hatch area on the dipstick.  Later I discovered that the dealership only put in 6 quarts of oil (when truck had about 19,000 miles).  Since this time, I've noticed the truck consuming oil, a good amount, between oil changes.  About 1 quart per 1,000.  I have never had to add oil between changes.

 

The dealer checked it and found no leaks anywhere, topped off the oil, and sent me on my way.  I asked for an oil consumption test.  They incorrectly performed an oil consumption test the first time.  The second time, fresh oil change, returned at 2,000 miles, and down 1.5 quarts of oil.  Returned again after 1500 miles and down another quart.  This is per the tech's documentation.  BUT, on the sheet, it is noted that TWO quarts of oil were used (qty 2 of part number 88865926).  The tech goes on to state, "the vehicle does show signs of being used to tow," and "per doc ID 6143939 this vehicle is consuming the normal amount of oil of quart per every thousand miles, this document also states it is normal for the vehicle to consume more than a quart every thousand miles when the vehicle is being used for towing or for highway usage due to higher than normal engine loads."

 

I have an RV and is the reason for buying the 2500 (who buys a 2500HD for pleasure - i.e., no hauling??).  HOWEVER, I had NOT towed anything nor any load beyond me and maybe my 120 pound son for 5 months before this latest oil consumption test.  No one asked me what driving I had been doing.  

 

I just recently returned from vacation with my RV.  I drove about 4,000 miles and about 3,000 miles was towing the RV (about 11,500 lbs).  Truck consumed 12 quarts of oil.  12!!!  Prior to reaching 19,000 miles, I drove the RV several times including long trips and the low oil never went off.  

 

BTW, no one is willing to scope the engine, pull the throttle body, nor check the PCV system.

[silveradosid]

do you see smoke coming out of the exhaust, if you used 12 quarts it should be smoking

[MachWun]

No Smoke.  And no evidence of it at the front of the RV.

Edited July 9, 2023 by MachWun

[KARNUT]

I’ve had three oil users. Two at a qt at 2500 miles and a used truck at 500 miles per qt. No smoking. I figured the cats prevented smoking. One had a bad cat at 60K miles. Strangely even at start up no smoke. If I didn’t witness it myself, I wouldn’t have believed it. 

[newdude]

On 7/8/2023 at 6:06 PM, MachWun said:

I have a 2020 Sierra 2500HD Denali with the Gasoline engine.  I did not have a problem or wasn't aware of one, until about a year ago.  Low oil light came about for the first time.  It took almost 3 quarts to get it into the cross hatch area on the dipstick.  Later I discovered that the dealership only put in 6 quarts of oil (when truck had about 19,000 miles).  Since this time, I've noticed the truck consuming oil, a good amount, between oil changes.  About 1 quart per 1,000.  I have never had to add oil between changes.

 

The dealer checked it and found no leaks anywhere, topped off the oil, and sent me on my way.  I asked for an oil consumption test.  They incorrectly performed an oil consumption test the first time.  The second time, fresh oil change, returned at 2,000 miles, and down 1.5 quarts of oil.  Returned again after 1500 miles and down another quart.  This is per the tech's documentation.  BUT, on the sheet, it is noted that TWO quarts of oil were used (qty 2 of part number 88865926).  The tech goes on to state, "the vehicle does show signs of being used to tow," and "per doc ID 6143939 this vehicle is consuming the normal amount of oil of quart per every thousand miles, this document also states it is normal for the vehicle to consume more than a quart every thousand miles when the vehicle is being used for towing or for highway usage due to higher than normal engine loads."

 

I have an RV and is the reason for buying the 2500 (who buys a 2500HD for pleasure - i.e., no hauling??).  HOWEVER, I had NOT towed anything nor any load beyond me and maybe my 120 pound son for 5 months before this latest oil consumption test.  No one asked me what driving I had been doing.  

 

I just recently returned from vacation with my RV.  I drove about 4,000 miles and about 3,000 miles was towing the RV (about 11,500 lbs).  Truck consumed 12 quarts of oil.  12!!!  Prior to reaching 19,000 miles, I drove the RV several times including long trips and the low oil never went off.  

 

BTW, no one is willing to scope the engine, pull the throttle body, nor check the PCV system.

 

Are they 100% on no leaks?  We've seen quite a few bad oil cooler lines on these new HD.  They are still on and off backorder from GM too due to their demand.  

 

They are using the correct document #6143939 which is for trucks at GVWR above 8600lbs. 

 

What they are not describing correctly and an important piece of information missing here is oil consumption per GM at 8600lbs GVWR and higher is NOT measured at the allowed limit of 1 quart per 2000mi, rather its 1qt for every 100 gallons of fuel used is the limit.  

 

So.  If you towed and used 100 gallons of gas, that's almost 3 full tanks.  Lets say you are getting 8mpg towing, that's 288mi per tank.  3 tanks of fuel, thats 864mi of driving.  At the weight you are pulling, you are also exposed to higher RPMs to maintain speed over say a 6000lbs trailer, and long standing higher RPMs with heavy load or high wind resistance can increase consumption. 

 

Here is the document they are referencing.  I've bolded some key areas including the most important part, the actual consumption test they should be using to document: 

 

03-06-01-023F: Higher Than Expected Oil Consumption at 8600 GVW and Above - (Aug 26, 2022)

 

Information on Engine Oil Consumption Guidelines

All engines require oil to lubricate and protect the load bearing and internal moving parts from wear including cylinder walls, pistons and piston rings. When a piston moves down its cylinder, a thin film of oil is left on the cylinder wall. During the combustion process, part of this oil layer is consumed. As a result, varying rates of oil consumption are accepted as normal in all engines.

 

Oil Consumption

Oil usage has a direct relationship with the amount of fuel used. The harder an engine works, the more fuel and oil it will use. Therefore, oil usage as a factor of fuel usage is a more accurate indicator of acceptable oil consumption levels than vehicle mileage for vehicles at or above 8600 GVW.

 

The accepted rate of oil consumption for gasoline engines in vehicles at or above 8600 GVW is 0.946 liter (1 qt) 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.

Many factors can affect an owner's concern with oil consumption. Driving habits and vehicle maintenance vary from owner to owner. Thoroughly evaluate each case before deciding whether the vehicle in question has abnormal engine oil consumption.

 

Gasket and External Leaks

Inspect the oil pans, engine covers, and the engine oil cooler for leakage. Inspect for oil leakage into the engine coolant.

Improper Reading of the Oil Level Indicator (Dipstick)

The vehicle must be parked on a level surface to obtain accurate oil level readings. Verify that the dipstick tube is fully seated in the block. When checking the oil level, make sure the dipstick is wiped clean before taking an oil level reading and fully depress the dipstick until the shoulder bottoms out on the dipstick tube. The dipstick should be the proper part number for the engine/vehicle that is being checked.

 

Not Waiting Long Enough After Running Engine to Check Oil Level

The vehicle should be allowed to sit for at least 15 minutes, after the engine has been shut off, before taking an oil level reading to assure the oil has had enough time to drain back into the crankcase. In order to ensure accurate results, the temperature of the oil should be close to the same temperature as the last time the oil level was checked.

 

Improper Oil Fill After an Oil Change

Following an oil change, verify that the proper amount and type of oil was put in the engine and that the oil level on the dipstick is not above the full mark or below the add marks. Refer to the Owner's Manual or Service Manual for information on recommended oil quantity, viscosity, and quality.

 

High Speed or High RPM Driving

Continuous driving at high speeds/high RPMs may increase oil consumption. Because this may not always be an everyday occurrence, it is hard to determine exactly how much the oil economy will be affected.

 

Towing or Heavy Usage

Towing a trailer or hauling additional weight will increase oil consumption. Large frontal area trailers will further increase the work required from the engine, especially at highway speeds, and thus increases the rate of oil consumption.

 

PTO Operation

Operation of a PTO will increase fuel and oil usage, as the PTO driven accessory uses engine power to operate.

 

Crankcase Ventilation System

Verify that the positive crankcase ventilation (PCV) system is operating properly. Blockages, restrictions or damage to the PCV system can result in increased oil use.

 

Oil Dilution from Condensation

On vehicles that are usually driven short distances, less than 8 km (5 mi), especially in colder weather, condensation generated from cold engine operation may not get hot enough to evaporate out of the oil. When this occurs, the dipstick may indicate that the oil level is over-full. Subsequent driving on a trip of sufficient length to enable normal engine operating temperature for 30 minutes or more, in order to vaporize excess moisture, may give the customer the impression of excessive oil consumption.

 

Engine Temperature

If an engine is run at overheated temperatures (see Owner's Manual or Service Manual) for more than brief periods, oil will oxidize at a faster than normal rate. In addition, gaskets may distort, piston rings may stick, and excessive wear may result. Verify that all cooling system components are in proper working order.

 

Engine Wear

Piston scuffing, excessive piston-to-wall clearance, tapered or out of round cylinders, worn, damaged or improperly installed valve guides, seals and piston rings will all cause an increase in oil consumption.

 

Measurement of Oil Consumption

Engines require a period of time to BREAK IN so that moving parts are properly seated. Therefore, 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 quarts) or more per 379 liters (100 gallons) of fuel used.

Verify that the engine has no external leaks. Repair as necessary.

Begin oil consumption test after next regularly scheduled oil and filter change. Oil changes should not be performed during the test.

Verify that the engine is at normal operating temperature (see Owner's Manual or Service Manual).

Park the vehicle on a level surface.

Wait at least 15 minutes, after the engine is shut off, before checking the oil level to make sure that most of the oil has had time to drain back into the crankcase.

Verify that the oil level is at, but not above, the full mark on the dipstick and that the proper viscosity and quality oil are being used as recommended in the Owner's Manual.

Dealer should record the vehicle mileage, date and engine hours at the start of the test on the form included in this bulletin.

 

Ask the customer to verify and record the date, odometer, oil level, fuel added, and engine hours, each time the vehicle is fueled, following steps 3-5 and return the vehicle to the dealership if the oil level is found at or below the add mark, 0.946 liter (1 qt) low, if possible. The dealer will add oil to return the oil level to full. If the oil level remains above the add mark, the customer should continue to operate the vehicle and verify the engine oil level until either the oil level drops to or below the add mark or at least 4800 km (3000 mi) has accumulated since the test began before returning to the dealership for a final evaluation.

 

If the final evaluation shows that the engine uses more than 0.946 liter (1 qt) in 379 liters (100 gallons) of fuel used, follow the published symptom diagnostics as described in the appropriate Service Manual. If the oil consumption test shows that the engine uses less than 0.946 liter (1 qt) in 379 liters (100 gallons) of fuel used, explain to the customer that their engine meets the guidelines for oil consumption.

Edited July 10, 2023 by newdude

[MachWun]

Lol,

1. They did not do any of this except add oil. 

2. By what is written, I have a problem.  I should have used half of the oil I did.

 

And the last tech they told me was a 'master cetified GM technician' or something like that.  Claimed there is so few in the country.  "He is so ****** about following process." 

[KARNUT]

My last  gas pulling rig was a V-10 I had two of those. Before that a 72 390 and a 65 2 ton wrecker converted to pull our equipment. It was a 6 cylinder with a two speed rear end and a granny stick. Started in 1988 we used mostly diesel for pulling. We pulled heavy our trucks 3/4 and 1 tons were registered for 25K combination. With the exception of 1 V-10 failure no oil usage ever, not a drop. Oil usage isn’t normal. Unless it’s a new phenomenon with these engines. In that case I wouldn’t call them new and improve. Lastly all our rigs were modified for horsepower. Still no oil usage. 

[MachWun]

New phenomenon.  Several MFGs (possibly all) have an acceptable amount of oil loss.  So now we need an accurate oil level gauge in vehicles just like the gas gauge since we will need to add oil every 3 tanks of gas.

 

I am 6' 4" and can't fill my oil without a step ladder.  This will suck in the Winter!