Is the N55 reliable?
We rate the N55 76 of 100 for reliability: good. The rating is one of the inputs to every Guide Score below, and it is argued for on the method page with the others.
Why that rating
The lit mark is the N55; each grey mark is another engine on the engines page.
Durable core with well-known, moderate-cost weak points: water pump and thermostat, valve cover and oil filter housing gaskets, VANOS solenoids, and the plastic charge pipe. Cheaper to keep healthy than any V8 here.
Cars in this guide with the N55
| Car | Years with this engine | Reliability | Guide Score |
|---|---|---|---|
| M2 F87 | 2016 to 2018 | 74 to 77 | 91 (2021) |
| M235i F22 | 2014 to 2016 | 76 to 77 | 74 (2016) |
| X4 M40i F26 | 2016 to 2018 | 80 to 81 | 55 (2018) |
Reliability is each car's score out of 100 for the years it had this engine: the engine rating plus that car's own known problems, service costs and age. The Guide Score is for the car's best year to buy.
Known problems on the N55
| Problem | Named in the guides for | Typical bill |
|---|---|---|
| Electric water pump and thermostat failure | M235i F22 | $1,500 |
| Valve cover and oil pan gasket leaks | M235i F22 | $1,300 |
| Water pump and thermostat failure | X4 M40i F26 | $1,000 |
| Oil leaks at the valve cover and oil filter housing | X4 M40i F26 | $750 |
| VANOS solenoid faults | X4 M40i F26 | $680 |
| Oil filter housing gasket leak | M235i F22 | $600 |
| Charge pipe cracking | X4 M40i F26, M235i F22 | $450 |
Bills are the guides' estimates, not quotes; each car's guide says which model years a problem hits and how to check for it. The bars share one scale, up to the costliest bill here.
Other engines
Every engine we rate, from the most reliable down, is on the engines page.