Nissan QR25 (QR family, 2.0 and 2.5)

Nissan's 2.5-litre four — the volume engine of the Altima, X-Trail and Rogue across four generations, and one of the highest-production engines in North America.

Oil consumption is the theme owners meet, particularly on earlier examples, where piston-ring and PCV-related consumption is common enough to be a pattern rather than an exception. It matters more than it would elsewhere because these cars are frequently run on long intervals: an engine that quietly uses oil and is checked twice a year is an engine that runs low, and low oil on a chain-driven engine accelerates chain and guide wear.

The timing chain, its tensioner and guides are therefore the second theme and the first is often its cause. Beyond that, catalytic-converter efficiency codes are common at high mileage on engines that have consumed oil — which is a consequence rather than an independent fault, and replacing the converter without addressing the consumption repeats it.