CriticalCommonEngine

Mazda Mazda6: 2.2 MZR-CD diesel injector seal failure, DPF clogging and oil dilution

2.2 MZR-CD diesel injector seal failure, DPF clogging and oil dilution is a common engine fault on the Mazda Mazda6 on the 2008–2012 cars, and we rate it critical. Putting it right costs $800 to $4,500 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 48 documented faults on the Mazda Mazda6.

Vehicle: Mazda Mazda6
Engine: 2.2L
Years: 2008–2012
Fuel: diesel
System: Engine

This page covers the Mazda Mazda6 as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All Mazda Mazda6 faults48 documented faults on this model

What you are looking at

What goes wrong

The GH's 2.2 MZR-CD diesel suffers leaking injector combustion washers (a chuffing noise and black tar around the injectors), a DPF that clogs on short-trip cars, and engine oil level rising above maximum as unburnt diesel from failed DPF regenerations dilutes the oil. Rising oil level is the dangerous one: ignored, it can damage the engine or in extreme cases cause runaway. These engines want open-road use and religious oil changes; a city-driven GH diesel is a money pit.

What you would notice

Chuffing or ticking from the top of the engine
Black sticky deposits around the injectors under the engine cover
DPF warning light or frequent regenerations (hot smell, raised idle)
Oil level above the max mark or oil smelling of diesel
Excess smoke after short-trip use

How to check it

Where to look. Injectors under the top engine cover; DPF in the exhaust under the car; dipstick for oil level

Pull the engine cover off (it just lifts) and look for black tar around the injector bases.
Check the dipstick: oil above max or smelling of diesel means walk away or budget thousands.
Ask what driving the car does — daily short commutes are a red flag.
Get evidence of oil changes at 10,000 km or less.

Parts involved: Fuel injector, Diesel particulate filter.

What it costs to put right

$800 to $4,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

“Has the oil level ever risen on its own between services?”
“Have the injector washers or DPF ever been replaced?”
“What sort of trips does the car mostly do?”

Now check the Mazda Mazda6 you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

mazda6club.com GH 2.2 diesel injector washer and oil dilution threads
HonestJohn.co.uk Mazda6 GH known-issues entries
AA / AU diesel buyer guides on MZR-CD DPF and oil dilution

Mazda Mazda6 buyer questions

Is 2.2 mzr-cd diesel injector seal failure, dpf clogging and oil dilution serious on a Mazda Mazda6?

We rate it critical and common on the Mazda Mazda6. The GH's 2.2 MZR-CD diesel suffers leaking injector combustion washers (a chuffing noise and black tar around the injectors), a DPF that clogs on short-trip cars, and engine oil level rising above maximum as unburnt diesel from failed DPF regenerations dilutes the oil. Rising oil level is the dangerous one: ignored, it can damage the engine or in extreme cases cause runaway. These engines want open-road use and religious oil changes; a city-driven GH diesel is a money pit.

How much does it cost to fix on a Mazda Mazda6?

$800 to $4,500 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which Mazda Mazda6 years are affected?

Our research records this fault on the 2008–2012 Mazda Mazda6. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Pull the engine cover off (it just lifts) and look for black tar around the injector bases. Check the dipstick: oil above max or smelling of diesel means walk away or budget thousands. Ask what driving the car does — daily short commutes are a red flag. Get evidence of oil changes at 10,000 km or less. Look here: Injectors under the top engine cover; DPF in the exhaust under the car; dipstick for oil level