BMW's turbocharged four-cylinder engines of the mid-2010s have developed a reputation for unreliability. That reputation comes from a number of different problems, the biggest of which—brittle plastic timing chain guides—caused a failure on this particular engine.
The I Do Cars YouTube channel managed to get its hands on a failed N26 four-cylinder for its latest teardown video, giving us an inside look at why so many of these engines fail. The leading theory is BMW's 15,000-mile oil change interval suggestion, allowing varnish and sludge to build up inside the engine while ruining the plastics and rubber.
This engine certainly supports this theory, going by the dark brown-stained metal in the head. Eric, the video's host, begins to find chunks of timing chain guide—which were plastic from the factory—as he digs deeper. His discoveries culminate at the oil pickup tube, which has been fully blocked by pieces of timing chain guide.
The chunks were plentiful enough to clog the oil's path to the pump, starving the engine of vital oil and eventually causing lots of wear and damage. Surprisingly many of the internals were salvageable, so at least it's not all bad news.
These days, BMW recommends changing the oil on its cars every 10,000 miles—far fewer than before, but still not the 5,000 to 7,000-mile interval that you probably should follow. If this teardown is any proof, oil changes should always be a priority. Otherwise, you'll be paying the price down the line.
