The 330e is a plug-in hybrid (PHEV), so it has a petrol engine and a smaller battery pack than a full EV (which runs exclusively on battery power). That means the BMW’s battery should be less expensive to replace if it ever needed to be.

At the moment, the world is waiting to find out how long EV batteries last, but it’s looking like between 10 and 20 years is going to be the magic number. A lithium-ion battery like this one will last longer if it’s never over-charged and is cycled regularly rather than left sitting for long periods.

There are two likely suspects here. The first is a blown head gasket which is allowing the oil and coolant to mix. Sometimes this shows up as oil in the coolant, sometimes as coolant in the oil. Sometimes both.

But before tearing the engine to pieces to change the gasket, it’s worth checking if the car is fitted with either an engine or transmission oil cooler. These often use the engine’s coolant to keep the oil or transmission fluid cool, and a failed one can allow the two fluids to mix, showing up as oil in the radiator or header tank.

The engine in the car you’re looking at has the codename N42. It has a timing chain rather than a rubber timing belt, so that should not need to be changed for the life of the car. However, life is not always that simple and the N42 has a bit of a reputation for developing wear in the tensioners that keep the timing chain taut. If that happens, you could have a chain loose enough to jump a few teeth on the timing gears and destroy the engine in the process. So a service record and close inspection of the engine is called for before any purchase.

This model BMW was also caught up in the Takata airbag recall debacle. As a result, many BMWs of this era were actually bought back by BMW and scrapped as the cost of fixing the airbag woes was greater than the value of the cars themselves. Make sure any car like this has had the airbags replaced and is not a candidate to be crushed rather than fixed. Quoting the car’s VIN to a BMW dealership should reveal all.