The N43 is a naturally aspirated 4 cylinder petrol engine, used between 2006 and 2013. It featured 2 variants, the N43B16 and the N43B20.

This engine suffers from a couple of reliability issues, such as the common timing chain guide issue where plastic pieces end up in the oil pickup leading to oil starvation. The N43 also suffers from injector, EGR and water pump issues, as well as NOx sensor problems.

The N46 and N42 engines are both valvetronic naturally aspirated 4 cylinder petrol engines. Although notoriously more reliable than the N43, they also suffer from timing chain slop, and the risk of oil starvation that comes with that's well as vanos problems. The valvetronic VVT system is also prone to problems.

The petrol 4 cylinder N45 has a few variants, the N45B16, used for the 1.6 pre-lci 1 series and the N45n used for only a couple of years for the 1.6l LCI 1 series, before being quickly replaced by the common N43. There is also a N45B20S engines, related to the others only by name, this is the homologation special engine used only in the 320si road engine making it a rare find. We have a whole 320si page for those interested in these cars.

In general these common N45 and N40 engines suffer from timing chain and hence oil starvation problems but if maintained well can be reliable.

The N12 and cousin N13 are turbo charged double vanos valvetronic engines, also known as the 'Prince Engines'.

Not renowned for their reliability, with timing chain problems (of course) and bad oil consumption, partnered with blue smoke from the exhaust indicating the valve stem seals are in need of replacement.

The N52 and N53 engines are both naturally aspirated 6 cylinder petrol engines.

The N52 is known as one of BMWs most reliable engines, with good servicing this engine should last a long time without giving you any headaches.

The N53 however is essentially the 6 cylinder version of the N43, suffering from all the same problems. Including timing chain problems, injector, EGR and water pump issues, and famously the NOx sensor.

The N54 is BMWs famous twin turbocharged 6 cylinder petrol engine, used for the 335i between 2007-2010 LCI version . These engines is well maintained will last a long time but you will need to keep on top of servicing, an often comes at a price. Various oil leaks are common, as well as injector failure, high pressure fuel pump (HPFP) problems, and of course the famous problem where the belt slips and comes in though the front main seal causing oil starvation, crazy we know! It wouldn't be hard to compile a list of problems with this car so we will make a blog post about this later.

The N55 is used in the later version of the 335i, F30. This again turbocharged 6 cylinder is significant more reliable Tham the N54. One thing to bear in mind is the rod bearing problem these cars have due to oil starvation. Due to poor baffling in the sumps, oil can slosh all to one side leaving the oil pickup exposed and dropping that oil pressure. Worth noting if you drive hard or on track. Rod bearings for these cars is something worth doing preventatively if the previous owner hasn't yet done so.

The diesels of the N series.

The N47 production began is 2007, being used on e8x, e9x, e6x and even as late at F10/F13 models.

This widely used 4 cylinder diesel is praised for its reliability and fuel efficiency. One of the main things to bear in mind is again...timing chain problems. Often overlooked or a blind eye is turned by the owner because timing chain cost for this engine is significantly more expensive than for its petrol counterparts. This is because the timing chain is situated on the back of the engine, making it hard to access.

N57 is the 6 cylinder diesel engine, suffering from high pressure fuel pump (HPFP) problems, as well as EGR valve failures and turbo problems. With these main issues addressed the N57 should give you not too much bother with reliability.