SH-VPTS 2.2 SkyActiv-D

An oil level that climbs above the maximum mark, a smell of diesel on the dipstick, and in later stages an oil warning or turbo and bearing wear. Each particulate filter regeneration injects extra fuel, and on short journeys the regeneration doesn't finish. Some of that fuel ends up in the sump, which raises the level and thins the oil. Mazda issued software updates and oil-level checks, but usage is still the deciding factor.

Check: Pull the dipstick and check the level against the marks, then smell it for diesel. Ask how the car was used and whether the software update has been applied, and walk away from a town car with a rising level.

Warning light, limp mode, oil level rising above the maximum mark from fuel dilution. The filter needs sustained hot running to regenerate. A car used for short urban trips never completes a regeneration cycle.

Check: Read the DPF soot load and the distance since the last regeneration on a scan tool, and check the engine oil level and smell it for diesel. Ask what the car was used for. A short-trip city diesel is the wrong car regardless of mileage.

Coolant loss with no visible external leak, white smoke, sweet smell. The EGR cooler cracks internally and leaks coolant into the intake. BMW recalled affected diesels over a fire risk from glycol deposits igniting.

Check: Check coolant level and look for unexplained top-ups in the service history. Verify the recall was carried out. It's free and searchable by VIN.