All About the BMW N55 Engine

The BMW N55 engine is the successor and replacement of the N54 engine. Like its predecessor, the N55 is a turbocharged 3.0L inline-6 cylinder engine known for its tremendous horsepower and fuel efficiency. Unlike the N54, the N55 uses a single twin-scroll turbocharger as opposed to the twin-turbo layout, allowing it to produce more power over a broader range.

But is the N55 a reliable engine, which models use it, and what exactly are the engine’s pros and cons?

Is the N55 Engine Reliable?

Yes, the N55 engine is one of the most reliable engines BMW has made. It greatly improves on old turbo inline six designs and is generally seen by car enthusiasts as a direct upgrade to its predecessor, the N54. Though it isn’t without its problems, namely the water pump and ignition coils that are prone to failure, the N55 is a solid engine that withstands the test of time — though it’s generally recommended to have certain parts such as the valve cover, the solenoids, oil cooler, thermostat, and fuel pumps replaced with compatible aftermarket parts for increased longevity and superior performance.

BMW Vehicles Equipped with the N55 Engine

The N55 engine can be found in various BMW models, including but not limited to the BMW 1 Series, BMW 3 Series, BMW 4 Series, BMW 5 Series, and the X series. Prominent models in particular include:

• BMW 135i E82 and E88 (2011-2013)
• BMW 335i F30, F34, and F31 (2012-2015)
• BMW 435i F32, F33, and F36 (2013-2016)
• BMW 535i F10, F11, and F07 (2011-2017)
• BMW X3 xDrive35i F25 (2011-2016)

N55 Engine Pros

The N55 engine is lauded as a reliable and effective engine largely because of its fuel efficiency, powerful performance, and variable camshaft timing system. Drivers also appreciate how easy it is to conduct oil changes with BMW models equipped with an N55 motor engine.

Easy Oil Change

The N55 engine has an oil filter housing that integrates the oil cooler, simplifying the oil change process. By making oil changes easier, it also becomes significantly less likely for oil leaks to occur in an N55 engine. It’s generally recommended to change the oil of an N55 engine every 5,000 to 7,500 miles, or once every year.

Increased Fuel Efficiency

Because the N55 engine has a direct injection system, it has fewer emissions and better fuel efficiency compared to other engine types. This is because fuel is injected directly into the combustion chamber, ensuring no fuel is wasted.

On top of that, the N55 engine also has an electric water pump that regulates the coolant flow according to the temperature of the engine. This reduces the parasitic drag on the engine and helps save fuel.

Powerful Performance

One of the biggest advantages the N55 engine has is that it is exceptionally powerful. This is largely because of its twin-scroll turbocharger — a turbocharger that splits cylinders into two groups to maximize the use of pulses in the flow of the exhaust gases in each cylinder. This reduces turbo lag and improves the throttle response and low-end torque.

The N55 also gets a power boost from its variable valve timing system, Valvetronic. This system adjusts the intake valve lift and duration, allowing it to optimize both airflow and engine performance.

VANOS

Vehicles occasionally have variable camshaft timing systems to help adjust the timing of the intake and exhaust valves, potentially improving fuel efficiency, reducing emissions, and optimizing engine performance. The N55 engine has such a system: VANOS, which draws its name from “Variable Nockenwellen Steuerung” — German for variable camshaft timing.

N55 Engine Cons

The N55 engine isn’t perfect. Some reported problems include its potential to overheat easily, the increased rate at which carbon builds up in the engine, spark plug and ignition coil failure, and the risk of oil leaks.

Overheats Easily

The electric water pump of the N55 engine is known to fail from time to time, occasionally without warning. If the pump fails, the risk of the engine overheating increases significantly.

When the engine overheats, the vehicle enters limp mode and becomes too slow to drive. Because of this, it’s important to inspect the electric water pump regularly and replace it every 60,000 miles, or every three to four years.

Prone to Carbon Buildup

Because of the vehicle’s direct injection system, carbon buildup increases, especially on the intake valves. This can cause problems, such as rough idling, engine misfires, power loss, and reduced fuel efficiency.

Spark Plug and Ignition Coil Degradation

N55 engines may be prone to accelerated spark plug and ignition wear. These are the components responsible for igniting the air-fuel mixture in the cylinders. When they become inoperative, problems such as misfires and lit check engine lights can manifest. Similarly, engine performance will decrease.

It’s strongly recommended to replace the spark plugs and ignition coils together once every 40,000 miles, or every three to four years.

Susceptible to Oil Leaks

Even if the oil filter housing is integrated into the oil cooler, the N55 engine is still susceptible to oil leaks, typically from the valve cover gasket or the oil pan gasket. This leads to increased oil consumption and thick smoke from the exhaust. If this problem is left unaddressed, a lack of engine oil means less lubrication in moving parts of the engine, increasing friction and potentially destroying them.