Engine code
The M20 is a SOHC straight-six petrol engine that Wikipedia says BMW built from 1977 to 1993. It sits between the four-cylinder M10 and the larger M30 six, and Wikipedia says the M20 began to be phased out after the M50 arrived in 1990. Wikipedia says its camshaft is driven by a timing belt, where the M10 and M30 use a chain.
BMW sold the M20 in US-market cars. BMW's parts data lists it in five US models: the E28 528e, the E30 325e, 325i and 325ix, and the E34 525i. Wikipedia says the 2.0 liter M20B20 and the 2.3 liter M20B23 were not sold in the United States.
Two kinds of M20 reached US buyers: the 'eta' engine built for economy in the 528e and 325e, and the 2.5 liter engine in the 325i and 525i. Version details and one open conflict are in At a Glance.
Quick read
- Ownership position: Not established yet. We are still researching this engine.
- Reliability: Not established yet. We are still researching this engine.
- Cost to own: Not established yet. We are still researching this engine.
- Power potential: Not established yet. We are still researching this engine. Factory outputs Wikipedia lists are in Technical Specifications.
- Main watch item: Not established yet. The cooling system recall under Known Failure Points is the only BMW-backed item we found.
M20 At a Glance
| Question | Practical answer |
|---|---|
| Sold in US-market BMWs | Yes. BMW's parts data lists the M20 in the 528e, 325e, 325i, 325ix and 525i for the US market. |
| Years built | Wikipedia says 1977-1993 worldwide. US-market cars in BMW's parts data were built from 09/1981 to 01/1993. |
| Layout | SOHC straight-six petrol with a cast iron block, an aluminum alloy head, two valves per cylinder and a timing belt, according to Wikipedia. |
| US versions | Wikipedia lists the 325i and 525i with the 2.5 liter M20B25 and the 528e with the 2.7 liter eta M20B27. Wikipedia lists the 325e with the M20B27 too, but BMW's fill-quantity data labels the 325e M20 B25, so that car's version is not settled here. |
| Engine oil capacity | BMW's fill-quantity data lists 4.25 liters (about 4.5 US quarts) for the US-market 325e, 325i and 525i, and 5.0 liters (about 5.3 US quarts) for the 325ix. The 528e is not established. |
| Reliability profile | Not established yet. We are still researching this engine. |
| Before buying | Confirm the exact version, because Wikipedia lists the 325e and 325i with different M20 versions and BMW's parts data splits several parts between earlier and later builds. |
Where you find it
BMW's parts data (the data we hold ends in December 2019) lists these US-market cars with the M20. Dates are BMW build dates. Wikipedia's application dates differ in places; these are BMW's.
| US model | Built |
|---|---|
| E28 528e | 09/1981-12/1987 |
| E30 325e | 10/1983-07/1988 |
| E30 325i | 12/1986-01/1993 |
| E30 325ix | 07/1987-01/1991 |
| E34 525i | 06/1988-08/1990 |
Technical Specifications
| Specification | Detail |
|---|---|
| Configuration | SOHC straight-six petrol, two valves per cylinder, rocker arm valve actuation |
| Block and head | Cast iron block, aluminum alloy head |
| Camshaft drive | Timing belt |
| Layout details | Bore spacing of 91 mm and a 20 degree slant in the engine bay, down from 100 mm and 30 degrees on the M10 and M30 family |
| M20B25 (325i, 525i) | 2,494 cc, 84 x 75 mm. The catalyst version is listed at 125 kW at 5,800 rpm, 226 Nm at 4,300 rpm and 8.8:1 compression, for 1987-1993. BMW's parts data marks the US 325i and 525i as catalyst cars. |
| M20B27 eta (528e, and 325e per Wikipedia) | 2,693 cc, 84 x 81 mm. Wikipedia gives 9.0:1 compression for the US M20B27ME and lists the M20B27ME at 121 hp and 170 lb-ft for models with a catalytic converter. For the 1988 model year it lists the US 325e and 528e 'Super Eta' at 8.5:1 and 127 hp at 4,800 rpm. |
| Not sold in the US | M20B20: 1,991 cc, 80 x 66 mm. M20B23: 2,316 cc, 80 x 76.8 mm. |
| Engine management | Not established yet. |
| Engine oil | 4.25 liters per BMW's fill-quantity data for the 325e, 325i and 525i, and 5.0 liters for the 325ix. BMW of North America's oil chart (SI B11 01 15, February 2017) lists 5W-30 LL01 or 0W-30 LL01FE for all BMW gasoline engines of model year 2011 and older; it does not name the M20 by code. |
| Firing order | 1-5-3-6-2-4, per BMW's Engine Technology training chart |
| Coolant | Not established yet. |
Factory Deep Dive
Block, head and layout
Wikipedia says the M20 uses a closed deck cast iron block with siamesed cylinder bores and a cross-flow aluminum alloy head. It also says the M20 shares the M10 and M30 layout of a single overhead camshaft with two valves per cylinder.
Timing belt
Wikipedia says BMW used a timing belt on the M20, instead of the chain used on the M10 and M30, to reduce noise and cost.
The eta engine
Wikipedia says the M20B27 was designed for efficiency and low-rev torque, with the e in 325e standing for eta, and that it was expressly developed with the American market in mind. It lists the 528e as the first car to use it, in 1982 on the US market.
Cylinder heads
Wikipedia lists three cylinder head castings used across the M20 run, numbered 200, 731 and 885. It says the 885 head was used on the M20B25 and, from 1988, on the M20B27.
Service Parts at a Glance
These numbers come from BMW's US parts data (December 2019). Dates are BMW build dates. Check the exact car before ordering.
| Part | BMW part number | Note |
|---|---|---|
| Oil filter | 11421707779 | Fits the 528e, 325e, 325i, 325ix and 525i. |
| Air filter element | 13721720861 | Fits the 528e, 325e, 325i, 325ix and 525i. Some 325e and 528e rows carry exhaust-type conditions. |
| Thermostat | 11531265085 | Fits the 325e (10/1983-09/1985) and 528e (09/1981-09/1985). BMW's data links it to 11531264668, also current. |
| Thermostat | 11531710953 | Fits the 325e and 528e from 09/1985, and the 325i, 325ix and 525i. |
| Exchange water pump | 11519070758 | Fits cars built from 09/1987: the 325e, 325i, 325ix, 525i and 528e. |
| Spark plug, Bosch WR9LS | 12121279599 | Six per engine. Fits the 325e (10/1983-07/1988) and the 528e (09/1981-12/1986). |
| Spark plug, Bosch W8LCR | 12129061869 | Six per engine. Fits the 325i and 325ix with a catalytic converter, the 525i, and the 528e built 12/1986-12/1987. |
| Ignition coil | 12131286087 | Fits the 528e, 325e, 325i, 325ix and 525i. |
| Cylinder head gasket, 1.75 mm | 11121722737 | Fits the 528e, 325e, 325i, 325ix and 525i. BMW's data also lists a 2.05 mm (+0.3) gasket, 11121722738. |
Known Failure Points and Service Items
Not established yet. We found no BMW service bulletin or training document for the M20.
01 Cooling system, 525i
NHTSA recall 98V-178 was received on 4 August 1998 and lists the 525i for model years 1989-1995. BMW's parts data lists the US 525i with the M20 for cars built 06/1988-08/1990. The recall record does not name an engine. The record says a failure of a coolant system component such as the thermostat, water pump or fan belt can raise coolant temperature and pressure. The remedy was a new design radiator cap.
Watch for: an overheating indication. The record's stated consequence is that hot coolant could be expelled if a heater core end piece cracked. NHTSA lists vehicles by model and model year, not by engine, and we cannot say whether a given car had the remedy done.
NHTSA's recall lookup returned no records for the 1985 528e, 1986 325e, 1987 and 1988 325i, and 1988 325ix. That is a sample check, not a complete search.
Reliability Verdict
Not established yet. We are still researching this engine.
Power Potential
Not established yet. We are still researching this engine.
Cost of Ownership
Not established yet. We are still researching this engine.
Common Questions
What BMW models had the M20 engine in the US?
BMW's parts data lists the M20 in five US-market models: the E28 528e (built 09/1981-12/1987), E30 325e (10/1983-07/1988), E30 325i (12/1986-01/1993), E30 325ix (07/1987-01/1991) and E34 525i (06/1988-08/1990).
Does the M20 have a timing belt or a timing chain?
Wikipedia says the M20 camshaft is driven by a timing belt.
How much oil does an M20 take?
BMW's fill-quantity data lists 4.25 liters, about 4.5 US quarts, for the US-market 325e, 325i and 525i, and 5.0 liters, about 5.3 US quarts, for the 325ix.
Did the US get the 2.0 liter or 2.3 liter M20?
No. Wikipedia says the 2.0 liter M20B20 was not sold in the United States (it was sold in Canada) and the 2.3 liter M20B23 was not sold in North America.
What is the difference between the 325e and the 325i engine?
Wikipedia lists the 325e with the 2.7 liter eta M20B27, tuned for low-rev torque, and the 325i with the 2.5 liter M20B25.
What replaced the M20?
Wikipedia lists the BMW M50 as the successor and says the M20 began to be phased out after the M50 arrived in 1990.
Sources
- Wikipedia, BMW M20
- NHTSA recall record 98V-178
- BMW parts catalog and fill-quantity data, data date December 2019 (internal reference, not linked)
- BMW of North America SI B11 01 15, Engine Oil Quick Reference Chart, February 2017 (NHTSA copy)
- BMW Engine Technology training, ST501: bmwrepairguide.com technical training PDF
