Oil Consumption Test
ENGINE COMPONENT TEST
Oil Consumption Test
The following diagnostic procedure is used to determine the source of excessive internal oil consumption:
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 liter (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.
1. Define excessive oil consumption, such as the number of miles driven per liter (quart) of oil used. Also determine customer's driving habits, such as sustained high speed operation, towing, extended idle and other considerations.
2. Verify that the engine has no external oil leak.
3. Verify that the engine has the 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. In no case should the level be above the top of the cross-hatched area and the letter "F" in FULL. If significantly overfilled, perform steps 5(1) through 5(4).
5. Perform an oil consumption test:
a. Drain engine oil, remove oil bypass filter and refill with one liter (quart) less than the recommended amount.
b. Run the engine for three minutes (10 minutes if cold), and allow oil to drain back for at least five minutes with vehicle on level surface.
c. Remove oil level dipstick and wipe clean. (Do not wipe with anything contaminated with silicone compounds.) Reinstall oil level dipstick being sure to seat the oil level dipstick firmly in the oil level indicator tube. Remove the oil level dipstick and draw a mark on the back (unmarked) surface at the indicated oil level. (This level should be about the same as the ADD mark on the face of the oil level dipstick.)
d. Add one liter (quart) of oil. Restart the engine and allow to idle for at least two minutes. Shut off the engine and allow oil to drain back for at least five minutes. Mark the oil level dipstick, using the procedure above. (This level may range from slightly below the top of the cross-hatched area to slightly below the letter "F" in FULL.)
e. Record the vehicle's mileage.
f. Instruct the customer to drive the vehicle as usual and:
i. Check the oil level regularly at intervals of 160 to 240 km (100-150 miles).
ii. Return to the service point when the oil level drops below the lower (ADD) mark on the oil level dipstick.
iii. Add only full liters (quarts) of the same oil in an emergency. Note the mileage at which the oil is added.
g. Check the oil level under the same conditions and at the same location as in steps 5(2) and 5(3).
i. Measure the distance from the oil level to the UPPER mark on the oil level dipstick and record.
ii. Measure the distance between the two scribe marks and record.
iii. Divide the first measurement by the second.
iv. Divide the distance driven during the oil test by the result. This quantity is the approximate oil consumption rate in kilometers per liter or in miles per quart.
h. If the oil consumption rate is unacceptable, go to step 6.
6. Check the positive crankcase ventilation (PCV) system. Make sure the system is not plugged. See Test 6: Positive Crankcase Ventilation (PCV) System.
7. Check for plugged oil drain-back holes in cylinder head and cylinder block.
8. If the condition still exists after performing the above tests, go to step 9.
9. Perform a cylinder compression test and/or a cylinder leak detection test. See. This can help determine the source of oil consumption such as valves, piston rings or other areas.
10. 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 the tips of spark plugs can be a clue to internal oil consumption. If internal oil consumption still persists, proceed as follows:
a. Remove engine from vehicle and place it on an engine work stand. See - Removal and Replacementfor 2.3L engine, see - Removal and Replacementfor 4.0L engine.
b. Remove the cylinder head and oil pan. See appropriate Mazda B-Series Engine Service Information.
c. Check piston ring clearance, ring gap and ring orientation. See appropriate Mazda B-Series Engine Service Information. Repair as required.
d. Check for excessive bearing clearance. See appropriate Mazda B-Series Engine Service Information. Repair as required.
12. Perform oil consumption test to confirm oil consumption concern has been resolved.
Excessive Engine Oil Consumption
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:
- Trailer towing applications
- Severe loading applications
- Sustained high speed operation
The following is a partial list of conditions that can affect oil consumption rates:
- Engine size
- Operator driving habits
- Ambient temperature
- Quality and viscosity of the oil
Operation under varying conditions can frequently be misleading. A vehicle that has been run for several thousand miles on short trips or in 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 liter (quart) of oil was used in about 160 km (100 miles). This perceived 160 km (100 miles) per liter (quart) oil consumption rate causes customer concern even though the actual overall oil consumption rate is about 2,400 km (1,500 miles) per liter (quart).
Make sure the selected engine oil meets Mazda specification and the recommended API performance category "SG" and SAE viscosity grade. It is also important that the engine oil is changed at the specified maintenance intervals for the typical operating conditions.