Is the B48 reliable?
We rate the B48 84 of 100 for reliability: strong. 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 B48; each grey mark is another engine on the engines page.
BMW's modular 2.0-liter turbo four, used here in its high-output versions: the B48A20T1 in the 2020 to 2024 M235i Gran Coupe and 2019 to 2022 X2 M35i, and from 2024 the B48A20T2, which adds port injection, in the X1 and X2 M35i and the M235 Gran Coupe.
The family has a good record with no pattern failure.
Its weak points are the ones BMW's modular engines share: coolant leaks from hoses, the thermostat and the water pump, oil filter housing and valve cover leaks (the housing is the subject of a proposed 2026 class action covering 2014 to 2021 cars with these engines), and carbon on the intake valves of the direct-injection-only versions; on these transverse cars the labor runs high.
Scored a notch below the B58, which has a longer record at high mileage.
Cars in this guide with the B48
| Car | Years with this engine | Reliability | Guide Score |
|---|---|---|---|
| X1 M35i U11 | 2024 to 2027 | 86 to 88 | 56 (2026) |
| X2 M35i U10 | 2024 to 2027 | 86 to 88 | 55 (2026) |
| X2 M35i F39 | 2019 to 2022 | 80 to 82 | 54 (2022) |
| M235i Gran Coupe F44 | 2020 to 2024 | 82 to 84 | 54 (2024) |
| M235 Gran Coupe F74 | 2025 to 2027 | 86 to 87 | 53 (2026) |
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 B48
| Problem | Named in the guides for | Typical bill |
|---|---|---|
| Oil filter housing and valve cover gasket leaks | X2 M35i F39, M235i Gran Coupe F44 | $1,700 |
| Coolant leaks | M235 Gran Coupe F74, X2 M35i F39, X1 M35i U11, M235i Gran Coupe F44, X2 M35i U10 | $1,200 |
| Valve cover and oil filter housing leaks | M235 Gran Coupe F74 | $900 |
| Intake valve carbon buildup | X2 M35i F39, M235i Gran Coupe F44 | $600 |
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.