Mercedes-Benz Diesel Engines Compared: OM603, OM604, OM605, OM606 and OM648
Mercedes-Benz diesel engines from the OM60x family and the later OM648 are some of the most popular engines we sell. They power classic W124, W210 and W202 models, and they are a favourite for swaps and turbo builds. This guide compares the OM603, OM604, OM605, OM606 and OM648 so you can see which engine suits your car or project.
Quick comparison
| Engine | Layout | Typical models | Best known for |
|---|---|---|---|
| OM603 | Inline six, 2 valves per cylinder | W124 300D Turbo, W126 300SD and 350SD | Classic turbo diesel, mechanical injection |
| OM604 | Inline four, 4 valves per cylinder | W202 C 220 Diesel, W210 E 220 Diesel | Compact and light |
| OM605 | Inline five, 4 valves per cylinder | W124 E 250 Diesel, W202, W210 | Five-cylinder balance of size and power |
| OM606 | Inline six, 4 valves per cylinder | W124 E 300 Diesel, W210 E 300 Turbodiesel, W463 G 300 | Strongest OM60x for performance builds |
| OM648 | Inline six, common-rail CDI | W211 E 320 CDI, W220 S 320 CDI | Modern common-rail six |
OM603: the classic six-cylinder turbo diesel
The OM603 is the older two-valve inline six used in the W124 and W126 turbo diesels. It uses mechanical injection, which makes it popular with owners who want a simple engine without complex electronics. Cylinder heads vary, so ask us which head an engine has before you buy. See our used OM603 turbo diesel engine.
OM604: the compact four-cylinder
The OM604 is the four-cylinder member of the family, with four valves per cylinder. It shares much of its design with the OM605 and OM606. It was mostly sold without a turbo, and builders often add one for a light, efficient project engine. See our OM604 diesel engine.
OM605: the five-cylinder middle ground
The OM605 adds a fifth cylinder and was offered with and without a turbo. It suits owners who want more torque than the OM604 in a shorter block than the OM606. See our OM605 2.5 turbo diesel engine.
OM606: the favourite for builds
The OM606 is the 3.0-litre, 24-valve inline six from the W124 E 300 Diesel and the W210 E 300 Turbodiesel. Its strong block and mechanical-pump versions make it the most popular choice for high-power diesel builds and engine swaps. Results depend on the parts used, so tell us your power goal and we will help you choose the right engine and kit. Browse our OM606 3.0L turbo diesel engine and the OM606 long block.
OM648: the common-rail six
The OM648 is a later inline six with common-rail CDI injection, used in models such as the W211 E 320 CDI and W220 S 320 CDI. It is a good fit for owners replacing an original OM648 who want the same engine back in the car. See our used OM648 turbo diesel engine.
Which engine should you choose?
- Replacing an original engine: buy the same engine code that left the factory in your car. Check the code on the block and your vehicle data card.
- Building a project or swap: the OM606 is the most popular choice, with the OM605 and OM604 as lighter options.
- Keeping it simple: the OM603 and mechanical-pump OM60x engines avoid most engine electronics.
Not sure which engine fits your car? Read Mercedes chassis codes explained, browse all Mercedes-Benz engines, or send us your VIN and we will confirm fitment.
