BMW 3 series E21 Technical data

Oil consumption can be measured after the engine has covered about 7500kms after rebuilding. Until then, it cannot be considered as stabilized.

The engine should not show oil leaks.

Maximum acceptable oil consumption: 0.15 liters/100kms

To evaluate oil consumption:

1. The value of oil consumption should be determined by weight (and not by volume).
2. Drain the oil from the vehicle at operating temperature. Emptying takes about 5 minutes.
3. Fill with new oil (weigh the amount of oil filled).
4. Drive the vehicle for 1000 kms.
5. Drain the oil at service temperature (5 minutes of draining).
6. Weigh the oil obtained.

(Consider the density of the oil at room temperature as 0.9)

Example:

Oil filled4500 grams – Drained oil obtained after 1000kms: 3600 grams

Oil consumed900 grams (considering density 0.9 => 1000 cc (1 liter oil 1000 kms => 0.1 l/ 100kms OK).

Possible causes of excessive oil consumption:

• Engine break-in not completely done.
• Defective or damaged valve stem seals.
• Piston/cylinder clearances.
• Piston rings damaged or incorrectly assembled.

• Excessive clearance between valve guide and valve stem.