BMW built the M20B25 from 1985 to 1993. It is a 2.5 L naturally aspirated petrol inline-6 with 170 hp and 226 Nm, part of the M20 family. You will find it in the BMW E30 325i, BMW E34 525i and BMW Z1.
This guide is about the M20B25 specifically: its specification, the cars that use it, how it differs from the other M20 versions, what to check, prices from our stock and fitment answers for each model. For the history of the whole family, read our M20 guide.
- Capacity and layout: 2.5 L, inline-6, naturally aspirated
- Output: 170 hp and 226 Nm
- Production: 1985–1993
- Fitted to: 3 models across 3 chassis generations
- In our stock: ask the desk for the next arrival
M20B25 specifications
| Item | Value |
|---|---|
| Engine code | M20B25 |
| Family | M20 |
| Capacity | 2.5 L |
| Layout | Inline-6 |
| Fuel | Petrol |
| Aspiration | Naturally aspirated |
| Power | 170 hp |
| Torque | 226 Nm |
| Specific output | 68 hp per litre |
| Production | 1985–1993 |
| Models | 3 |
Built from 1985 to 1993, the M20B25 displaces 2.5 L in an inline-6 layout and is naturally aspirated. It produces 170 hp and 226 Nm on petrol. That is about 68 hp and 90 Nm per litre, a relaxed tune aimed at torque, durability and economy. Within the M20 family, it is the most powerful version, while the M20B20 (129 hp), M20B23 (139 hp) and M20B27 (125 hp) are milder. It was fitted to the BMW E30 325i, BMW E34 525i and BMW Z1.
What the code M20B25 means
- M marks an M-series code, the naming BMW used for its engine families up to the early 2000s.
- 20 is the family number.
- B stands for petrol (from the German Benzin).
- 25 is the capacity in decilitres, so 2.5 litres.
Which BMW models use the M20B25
| Model | Generation | Built |
|---|---|---|
| BMW E30 325i | second 3 Series | 1982–1994 |
| BMW E34 525i | third 5 Series | 1988–1996 |
| BMW Z1 Z1 | Z1 roadster | 1989–1991 |
In the E30 second 3 Series (1982–1994), the M20B25 powered the 325i. Engines from other models fit the E30 as long as the sump, mounts and ancillaries match, which we check against your VIN. All E30 engines
In the E34 third 5 Series (1988–1996), the M20B25 powered the 525i. Engines from other models fit the E34 as long as the sump, mounts and ancillaries match, which we check against your VIN. All E34 engines
In the Z1 Z1 roadster (1989–1991), the M20B25 powered the Z1. Engines from other models fit the Z1 as long as the sump, mounts and ancillaries match, which we check against your VIN.
M20B25 compared with other M20 versions
| Code | Capacity | Power | Torque | Years |
|---|---|---|---|---|
| M20B20 | 2.0 L | 129 hp | 164 Nm | 1977–1992 |
| M20B23 | 2.3 L | 139 hp | 205 Nm | 1977–1987 |
| M20B27 | 2.7 L | 125 hp | 240 Nm | 1982–1988 |
| M20B25 | 2.5 L | 170 hp | 226 Nm | 1985–1993 |
M20B25 or M20B23?
The M20B23 has 31 hp less than the M20B25 (139 against 170 hp), from 2.3 L instead of 2.5 L, and was built 1977–1987. A different capacity means a different crankshaft, pistons or head, and different software. It can be fitted as an upgrade with the matching engine control unit and wiring, but it is a conversion rather than a straight replacement.
M20B25 or M20B20?
The M20B20 has 41 hp less than the M20B25 (129 against 170 hp), from 2.0 L instead of 2.5 L, and was built 1977–1992. A different capacity means a different crankshaft, pistons or head, and different software. It can be fitted as an upgrade with the matching engine control unit and wiring, but it is a conversion rather than a straight replacement.
M20B25 or M20B27?
The M20B27 has 45 hp less than the M20B25 (125 against 170 hp), from 2.7 L instead of 2.5 L, and was built 1982–1988. A different capacity means a different crankshaft, pistons or head, and different software. It can be fitted as an upgrade with the matching engine control unit and wiring, but it is a conversion rather than a straight replacement.
Common M20B25 problems
The M20B25 shares its weak points with the rest of the M20 family. These are the faults to check on a used unit and on your own engine. The full explanation of each is in the M20 guide.
| Known fault | What to check |
|---|---|
| Timing belt failure | Ask for the date of the last belt and tensioner change. If there is no record, treat it as due. |
| Cylinder head cracks | Pressure-test the cooling system and look for cracks when the cam cover is off. |
| Rocker arm and shaft wear | Inspect rockers and clips with the cam cover removed. |
| Oil spray bar and cam wear | Check the spray bar banjo bolts are tight and the holes clear. |
| Water pump and thermostat | Look for coolant trails below the pump and on the belt cover. |
Rocker arm and shaft wear. Rocker arms can crack and the retaining clips can walk off the shaft. The 'rocker arm fix' with improved clips is a known upgrade.
M20B25 maintenance
- 10W-40 or 15W-40 semi-synthetic, about 4.25 litres with filter.
- Oil every 7,500 km; valve clearances every 15,000 km; belt on time, not only on distance.
- Rubber timing belt with tensioner, changed with the water pump every 60,000 km or four years.
Will the M20B25 fit my car?
Will the M20B25 fit my BMW Z1 Z1?
Yes, the BMW Z1 Z1 left the factory with the M20B25, so an M20B25 from another car is the direct replacement. The Z1 roadster was built 1989–1991, and the M20B25 was produced 1985–1993, so check that your car's build date falls inside that window. Confirm the drive type (rear-drive or xDrive), the gearbox (manual or automatic) and the emissions standard, because these can change the sump, the flywheel and the software. Send us the VIN and we check all of it for you.
How much is a replacement engine for a BMW Z1 Z1?
We do not have an M20B25 on the shelf for the Z1 Z1 at the moment. Units arrive regularly; send us your VIN and we will tell you when the next one is ready and what it will cost, including delivery.
M20B25 prices
We do not have an M20B25 on the shelf at the moment. Send us your VIN or the code you need and the desk will tell you when the next unit arrives and what it will cost.
Buying a used M20B25: checklist
- Gearbox and flywheel match. Manual and automatic engines differ at the flywheel or flexplate, and sometimes at the crankshaft spigot. Make sure the engine you buy matches your gearbox or that you transfer the right parts.
- Why your old engine failed. Before fitting a replacement, find out why the original failed. An overheating radiator, a blocked intercooler or a failed turbo can destroy a second engine if they are not fixed.
- Compression or leak-down figures. Even compression across all cylinders tells you more than mileage. Ask for the figures, not just a pass or fail, and compare the highest and lowest readings: a spread above 10 to 15 percent deserves a question.
- List of what is fitted. Engines are sold with different ancillaries: some have the turbo, injectors, manifolds, alternator and starter, others are long blocks. Agree the list in writing so you know which parts must come from your old engine.
- Look at the oil and coolant. Clean oil without metal particles and coolant without oil are good signs. Milky oil, oily coolant or a burnt smell mean the engine needs further checks before it is fitted.
- Timing belt history. A timing belt must be changed on time and distance. With no dated record, treat the belt, tensioner and water pump as due and replace them before the first start.
- Originality and numbers. For collectible cars, the engine number and correct ancillaries add value. Photograph the stamp and keep it with the car's documents.
Questions about the M20B25
How do I know a used M20B25 engine is in good shape?
Before a unit is listed, the yard checks the engine code against the listing, writes down the parts fitted to it, seals every opening and photographs the real engine you will receive. An inspection certificate for the unit can travel with the order when you ask for it.
When you look at a listing, check the recorded mileage, the year and the photos of the ports and the stamp. Ask for photos of anything you want to see closer. Ask the desk for more pictures of any listing. We are happy to show the stamp, the ports and the ancillaries before you decide.
On a petrol engine like the M20B25, a careful fitter will also look at the spark plugs, the coils and the timing side before the engine goes in.
If the engine fails inside under normal use, the warranty covers you. Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop.
See all M20 Engines · Search M20B25 in the shop
Will the M20B25 engine fit my BMW E28 525i?
Yes, if your BMW E28 525i was built with the M20B25. BMW used this 2.5 liter (2,494 cc) petrol engine with 126 kW (171 HP) in the E28 525i from about 1985 to 1993.
In our records the M20B25 is the engine for the E28 525i, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your E28 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
How much is a replacement M20B25 engine for a BMW E34 525i?
A used M20B25 for the BMW E34 525i costs from about 1.300 € to 2.200 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.
A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B25 you buy is photographed and checked in Hamburg before it is listed.
Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
Will the M20B25 engine fit my BMW E34 525i?
Yes, if your BMW E34 525i was built with the M20B25. BMW used this 2.5 liter (2,494 cc) petrol engine with 126 kW (171 HP) in the E34 525i from about 1985 to 1993.
Some E34 525i cars were built with a different engine: the M50B25. These look alike from the outside, so check the code on your engine or send us your VIN.
Also tell us if your E34 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
What is the difference between the M20B25 and other M20 engines?
The M20B25 makes 126 kW (171 HP) and 226 Nm. The other M20 engines are: M20B20 with 95 kW (129 HP) and 174 Nm (1977 to 1992).
Engines in one family share a basic block, but the turbo, the injection, the sensors and the engine computer can differ. A higher power version often has different pistons, a bigger turbo or a different fuel system.
This is why we ask for the exact code. Fitting a different version can work, but the wiring, the software and sometimes the gearbox must be changed to match.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
What is the BMW M20B25 engine?
The BMW M20B25 is a 2.5 liter (2,494 cc) petrol engine from the M20 family. It has an inline 6, SOHC, 12 valve layout with no turbo (naturally aspirated), and makes 126 kW (171 HP) with 226 Nm of torque. BMW built it from 1985 to 1993 and it meets the Euro 1 emission standard.
You find the M20B25 in the BMW E30 325i, BMW E30 325is, BMW E28 525i, BMW E34 525i and BMW Z1. What we list: BMW M20 small-six petrol engines for E30 and E28.
At Autowerke Engines every M20B25 is a real used engine from our yard in Hamburg. The photos on each listing show the actual engine, not a stock picture. The yard checks the code, records what is bolted on, and seals the openings before the engine is offered. Each listing shows the year, the mileage and the price, so you can compare units side by side.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
How much power and torque does the BMW M20B25 have?
From the factory the BMW M20B25 makes 126 kW (171 HP) and 226 Nm of torque. It is a 2.5 liter (2,494 cc) inline 6, SOHC, 12 valve petrol engine with no turbo (naturally aspirated).
Without a turbo, the power builds smoothly with the revs. A clean air intake, healthy ignition and the correct fuel are key to getting the full figure.
A used engine reaches its factory numbers when it is fitted with the matching engine computer and software, and serviced with the right oil and filters. If the engine computer from your car is a different version, a specialist may need to code it.
Every M20B25 on our site lists its year and mileage. Ask the desk for more pictures of any listing. We are happy to show the stamp, the ports and the ancillaries before you decide.
See all M20 Engines · Search M20B25 in the shop
Which cars use the BMW M20B25 engine?
BMW fitted the M20B25 to the BMW E30 325i, BMW E30 325is, BMW E28 525i, BMW E34 525i and BMW Z1. These cars were built with this engine from about 1985 to 1993.
The badge on the boot is not enough to be sure. The same model name can hide two different engines, for example after a facelift or a change in emission rules. Always read the engine code stamped on the block, or look it up with your VIN.
Other engines in the same M20 family are the M20B20 (129 HP). They look alike but differ in power, parts and electronics, so they are not always a direct swap.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
How much is a replacement M20B25 engine for a BMW E30 325is?
A used M20B25 for the BMW E30 325is costs from about 1.300 € to 2.200 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.
A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B25 you buy is photographed and checked in Hamburg before it is listed.
Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
Will the M20B25 engine fit my BMW Z1?
Yes, if your BMW Z1 was built with the M20B25. BMW used this 2.5 liter (2,494 cc) petrol engine with 126 kW (171 HP) in the Z1 from about 1985 to 1993.
In our records the M20B25 is the engine for the Z1, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your Z1 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
How much does a used BMW M20B25 engine cost?
A used BMW M20B25 engine in our yard usually costs between 1.300 € and 2.200 €. The exact price depends on the year, the mileage and the parts that come with the engine.
Our units show recorded mileage from about 22,000 km up to around 200,000 km. Lower mileage and more ancillaries mean a higher price. Each listing shows its own price, and the price you see is the price you pay. Prices include VAT for private buyers.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. If you order a gearbox or a second engine on the same order, the fee is still charged once.
Inside the EU there is no import duty. For the UK and other non-EU countries, import duty and local VAT are paid by the receiver, and we supply a commercial invoice.
See all M20 Engines · Search M20B25 in the shop
How long does delivery of an M20B25 engine take?
Orders confirmed before 14:00 CET on a working day leave Hamburg the same day. Later and weekend orders leave the next working day. Delivery to the Netherlands, Belgium, Germany, France, Luxembourg and Denmark takes 1 to 3 working days.
Spain, Italy, Portugal, Poland, Czechia, Austria, Ireland, the Nordics and the Baltics take 2 to 5 working days. Greek and Spanish islands, Malta, Cyprus and remote areas take 4 to 8 working days. The UK and other countries outside the EU are quoted one by one.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Every engine is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped, then photographed before it leaves the yard.
You get a tracking number when the pallet is collected. Check the wrapping before you sign, and note any damage on the paperwork.
See all M20 Engines · Search M20B25 in the shop
How much is a replacement M20B25 engine for a BMW E30 325i?
A used M20B25 for the BMW E30 325i costs from about 1.300 € to 2.200 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.
A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B25 you buy is photographed and checked in Hamburg before it is listed.
Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
What should I replace when I fit a used M20B25 engine?
A used engine lasts longest when it starts life in your car with fresh fluids and new seals. Fit a new oil filter and fresh oil of the grade BMW lists for this engine, and refill the coolant with the correct BMW antifreeze mix. Change the drive belt, the thermostat and the water pump seals if they look tired, because they are cheap while the engine is out. Use new gaskets for the exhaust manifold, the intake and the sump plug, and check every hose clip before the first start.
Look at the engine mounts and the clutch or the torque converter while the engine is out. Old mounts can crack a new engine's brackets, and a worn clutch is much easier to change now.
Before the first start, turn the engine over without fuel until the oil pressure light goes out. Then let it idle, check for leaks, and drive gently for the first few hundred kilometres.
The warranty asks for fitting by a qualified mechanic and the correct oil, coolant and filters. Keep your receipts in case you ever need to make a claim.
See all M20 Engines · Search M20B25 in the shop
How much is a replacement M20B25 engine for a BMW Z1?
A used M20B25 for the BMW Z1 costs from about 1.300 € to 2.200 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.
A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B25 you buy is photographed and checked in Hamburg before it is listed.
Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
How much is a replacement M20B25 engine for a BMW E28 525i?
A used M20B25 for the BMW E28 525i costs from about 1.300 € to 2.200 € in our yard. The price depends on the year, the mileage and the parts that come with the engine.
Shipping is a flat 249 € per order. It is added once at checkout and printed on the invoice, so there is no extra fee later. Inside the EU there is no import duty. Outside the EU, the receiver pays local duty and VAT.
A replacement engine is often much cheaper than rebuilding a damaged one, and much faster. The M20B25 you buy is photographed and checked in Hamburg before it is listed.
Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop. Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
Can you check if an M20B25 fits my car with my VIN?
Yes, and it is free. Send the 17-character VIN of your car and, if you have it, the gearbox code. We check the engine family, the build year window and the parts your car needs.
For the M20B25, we confirm that your car was built with this code or with a version that can take it. BMW used it in the BMW E30 325i, BMW E30 325is, BMW E28 525i, BMW E34 525i and BMW Z1.
We only reserve an engine once the match is confirmed, so you never pay for the wrong unit. You can reach the Hamburg desk by email at autowerkeengines@gmail.com, or by phone and WhatsApp on +49 15510 030835, Monday to Friday, 9:00 to 16:00 CET.
You can also use the VIN check on our site. It reads the year, the make, the model and the engine from the public vehicle register.
See all M20 Engines · Search M20B25 in the shop
Is the BMW M20B25 a diesel or petrol engine?
The M20B25 is a petrol engine. It is a 2.5 liter (2,494 cc) inline 6, SOHC, 12 valve unit with no turbo (naturally aspirated), and it was built to the Euro 1 emission standard.
The emission standard matters for registration and for low-emission zones in many cities. When you replace an engine with the same code, the car keeps the same paperwork and the same emission class.
Petrol versions need the correct catalytic converters and oxygen sensors on the car to stay legal and to keep the engine computer happy. Reuse the parts from your car if they are in good condition.
If you are not sure which version you need, send us your VIN. We tell you the right code for free.
See all M20 Engines · Search M20B25 in the shop
Will the M20B25 engine fit my BMW E30 325i?
Yes, if your BMW E30 325i was built with the M20B25. BMW used this 2.5 liter (2,494 cc) petrol engine with 126 kW (171 HP) in the E30 325i from about 1985 to 1993.
In our records the M20B25 is the engine for the E30 325i, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your E30 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
What comes with a used M20B25 engine?
Each M20B25 is sold as described on its own listing. The yard writes down the parts that are fitted to that unit, such as the turbo, the injectors, the manifolds or the alternator, so you know what arrives.
Some units are long engines with few ancillaries, others are more complete. If you need a part that is not listed, ask the desk. We often have the matching items in the yard.
Every engine is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped, then photographed before it leaves the yard.
On delivery, the carrier brings the pallet to the kerb or a loading bay. Please have a forklift, a pallet truck or an engine crane ready.
See all M20 Engines · Search M20B25 in the shop
Does a used M20B25 engine come with a warranty?
Yes. Eligible engines come with a 12 months warranty from the delivery date. It covers internal mechanical failure under normal use and correct fitting by a qualified mechanic or workshop.
The warranty does not cover damage from wrong fitting, overheating, low oil, wrong fluids or fuel, engines that were opened or modified without our approval, or labour and towing costs.
To claim, send us your order number, a short description of the problem, photos or a video, and a mechanic's report if we ask for one. If the claim is approved, we repair, replace or refund the engine.
Keep the receipts for the fitting, the oil and the filters. They make any claim quick and simple.
See all M20 Engines · Search M20B25 in the shop
Will the M20B25 engine fit my BMW E30 325is?
Yes, if your BMW E30 325is was built with the M20B25. BMW used this 2.5 liter (2,494 cc) petrol engine with 126 kW (171 HP) in the E30 325is from about 1985 to 1993.
In our records the M20B25 is the engine for the E30 325is, which makes the match simple. Still, check the code on your old engine or send us your VIN.
Also tell us if your E30 has a manual or an automatic gearbox. The flywheel or the flex plate and some sensors depend on it.
Not sure? Send us your VIN and your gearbox code. We match the engine family, the year window and the parts on the engine before anything is reserved, and the check is free.
See all M20 Engines · Search M20B25 in the shop
Delivery, warranty and payment
Every M20B25 we sell is drained, sealed at each opening, strapped to a heat-treated pallet and shrink-wrapped before it leaves Hamburg. You receive photographs of the packed engine and a tracking number.
Delivery is door to door and included in the price. Most European addresses receive the engine within five to ten working days; Germany and its neighbours are usually faster.
Every engine carries a 12-month warranty on eligible internal failure when a qualified workshop fits it with new fluids and filters. Payment is by card, bank transfer or crypto; your invoice is emailed as soon as you order.
