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Oil Leakage & Consumption 

Leak Locations:  Underhood | Under Engine
Oil Loss & Tests:  Information | Oil Consumption Test | Oil Pressure Test

Oil Leakage Locations

Underhood valve cover gaskets intake manifold gaskets cylinder head gaskets engine front cover gasket camshaft position sensor O-ring oil level indicator tube connection oil pressure sensor oil bypass filter

Under Engine oil pan gasket oil pan front and/or oil pan rear seal crankshaft front seal crankshaft rear oil seal

Excessive Oil Loss and Tests

The amount of oil an engine uses will vary with the way the vehicle is driven in addition to normal engine-to-engine variation. This is especially true during the first 16,100 km (10,000 miles) when a new engine is being broken in or until certain internal engine components become conditioned. Vehicles used in heavy-duty operation may use more oil. The following are examples of heavy-duty operation:

Engines need oil to lubricate the following internal components: When the pistons move downward, a thin film of oil is left on the cylinder walls. The oil is burned away on the firing stroke during combustion. If an engine burned a drop of oil during each firing stroke, oil consumption would be about one quart for every mile traveled. Fortunately, modern engines use much less oil than this example. However, even efficient engines will use some oil or they would quickly wear out. As the vehicle is operated, some oil is also drawn into the combustion chambers past the intake and exhaust valve stem seals and burned.

Many different conditions can affect oil consumption rates. The following is a partial list of these items:

Operation under varying conditions can frequently be misleading. A vehicle that has been run for several thousand miles on short trips or below-freezing ambient temperatures may have consumed a "normal" amount of oil. However, when checking the engine oil level, it may measure up to the full mark on the oil level dipstick due to dilution (condensation and fuel) in the engine crankcase. The vehicle then might be driven at high speeds on the highway where the condensation and fuel boil off. The next time the engine oil is checked, it may appear that a quart of oil was used in about 160 km (100 miles). This perceived 160 km (100 miles) per quart of oil consumption rate causes customer concern even though the actual overall oil consumption rate was about 2400 km (1500 miles) per quart.

Make sure the selected engine oil meets the recommended API performance category "SH" and SAE viscosity grade as shown in the vehicle Owner Guide. It is also important that the engine oil is changed at the intervals specified for the typical operating conditions.

Oil Consumption Test

The following diagnostic procedure is intended to be used to determine the source of excessive internal oil consumption:

1. Note: Oil use is normally greater during the first 16,100 km (10,000 miles) of service. As mileage increases, oil use generally decreases. Vehicles in normal service should get at least 1,450 km (900 miles) per quart after 16,100 km (10,000 miles) of service. High speed driving, towing, high ambient temperature and other factors may result in greater oil use.

Define excessive oil consumption such as how many miles are driven per quart of oil. Also determine owner's driving habits such as sustained high-speed operation, towing, extended idle and other factors.
2. Verify engine has no external oil leak as described under «Engine Oil Leaks».
3. Verify engine has correct oil level dipstick.
4. Verify that the engine is NOT being run in an overfilled condition. Check the oil level at least five minutes after a hot shutdown with the vehicle parked on a level surface. The oil level should never be above the top of cross-hatch area and "F" in FULL. If significantly overfilled, perform Steps 5a through 5d.
5. Perform an oil consumption test:

6. Check PCV valve system. Make sure system is not plugged.

7. Check for plugged oil drain-back holes in cylinder heads and cylinder blocks.

8. If the condition still exists after performing the above tests, go to Step 9.

9. Perform a Compression Test (below), and/or an Oil Leak and Valve Guide Seal Test as described, with Rotunda Pressurization Kit 014-00705 or equivalent. This can help to determine the source of oil consumption such as valves, piston rings or other areas.

10. Note: After checking for worn parts, determine which parts should be replaced. Use correct parts. Check valve guides for excessive guide clearance. Replace all valve stem seals after verifying valve guide clearance.

11. Worn or damaged internal engine components can cause excessive oil consumption. Small deposits of oil on tip of spark plugs can be a clue to internal oil consumption. If internal oil consumption still persists, proceed as follows:

12. Perform oil consumption test as described to confirm oil consumption concern has been resolved.

Oil Pressure Test

Description Tool Number
Engine Oil Pressure Gauge T73L-6600-A
1. Disconnect and remove the oil pressure sensor from the engine.

2. Connect an Engine Oil Pressure Gauge T73L-6600-A and Transmission Test Adapter D87C-77000-A or equivalent to the oil pressure sender oil galley port.

3. Run the engine until normal operating temperature is reached.

4. Run the engine at 3,000 rpm and record the gauge reading.

5. The oil pressure should be:

6. If the pressure is not within specification, check the following possible sources:

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