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Mike, Master Technician
Category: Chevy
Satisfied Customers: 81
Experience:  25 years GM experience, owned my own diagnostic shop for 8 years. ASE Master Tech, ASE L1 Advanced
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I HAVE A CHEVY VORTEC 8.1 LITER ENGINE, WHY DOESNT MY

Resolved Question:

I HAVE A 2002 SILVERADO 2500 HD WITH A VORTEC 8.1 LITER ENGINE, WHY DOESN'T MY ENGINE HAVE A PCV VALVE? THE CRANKCASE VENTS THROUGH THE INTAKE MANIFOLD AND THROUGH THE THROTTLE BODY TO THE FRONT OF THE BUTTERFLY VALVE. IS THIS WHY MY ENGINE USES OIL? A QUART ABOUT EVERY 1500 MILES OR SO. IT HAS DONE THIS SINCE IT WAS NEW,THE TRUCK RUNS GREAT BUT I'M WORRIED ABOUT THIS OIL PLUGGING MY CATALYTIC CONVERTERS. WHAT DO YOU THINK?
Submitted: 7 years ago.
Category: Chevy
Expert:  replied 7 years ago.

Hello Big Red,

Many engines today do not use a PCV system however all perform the same function. What a PCV system does is pull crankcase vapors through the valve into the intake manifold to burn them. Your system uses a very precisely measured orifice tube which serves the same function. It will not cause it to burn more or less oil than the PCV valve equipped system. So as you can see both pull vapors into the manifold just in a different way. Now for the consumption of your oil. It sounds like you have been informed somewhat that this amount of oil is considered normal by GM and that is accurate. Here is their consumption chart to determine if there is a problem and you will see their suggestions. It is fairly common to experience this but is vehicle dependant, meaning another of the exact model may be different. Also with that consumption level it will likely do no harm to the converters.

nfo - Higher Than Expected Oil Consumption (Greater Than 8500 GVW) #03-06-01-023 - (08/19/2003)

Table 1:Calculation:
Higher Than Expected Oil Consumption >8500 GVW

2000-2004 Chevrolet Express, Silverado, Suburban

2002-2004 Chevrolet Avalanche

2000-2004 GMC Savana, Sierra, Yukon XL

2003-2004 Chevrolet Kodiak C4500-C5500 Series Models

2003-2004 GMC Topkick C4500-C5500 Series Models

2003-2004 HUMMER H2

with Gasoline Engines and Rated at 8600 GVW and above

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.

  1. Verify that the engine has no external leaks. Repair as necessary.
  2. Begin oil consumption test after next regularly scheduled oil and filter change. Oil changes should not be performed during the test.
  3. Verify that the engine is at normal operating temperature (see Owner's Manual or Service Manual).
  4. Park the vehicle on a level surface.
  5. 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.
  6. 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.
  7. Dealer should record the vehicle mileage, date and engine hours at the start of the test on the form included in this bulletin.
  8. 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.
  9. 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.

Oil Consumption Worksheet

Owner Name

Location

Dealer Name

Dealer Code

Assign TAC

TAC Case #

Engine Model

Serial #

VIN

Oil Brand

Oil Viscosity

Fuel Brand

DATE

ODOMETER READING

ENGINE HOURS

FUEL QUANTITY ADDED

OIL QUANTITY ADDED

Start

--------------

--------------

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

Total

Calculation:

System

Oil Used

/

Fuel Used

=

Qt/Gal or L/L

*

=

Oil Consumption

Qt/100 Gal

L/379L

English

 

/

 

=

 

*

100

=

Metric

 

/

 

=

 

*

379

=

Oil consumption of 0.946L/379L of fuel (1 qt./100 gal.) or less is considered acceptable.

 

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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© Copyright General Motors Corporation. All Rights Reserved.


Document ID#(NNN) NNN-NNNN
2002 Chevrolet Chevy C Silverado - 2WD

 

 

 

 

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Thank you, Mike

Mike, Master Technician
Category: Chevy
Satisfied Customers: 81
Experience: 25 years GM experience, owned my own diagnostic shop for 8 years. ASE Master Tech, ASE L1 Advanced
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