When I asked the garage whether the oil could be contaminated, I was told it wasn't. When I asked how they knew that they said because the dpf parameters were OK. So apparently no physical examination of the oil has taken place.
It’s an estimated value – not actual. Examiner (or alternative – my garage uses Omitec) will indicate oil degrade by percentage. When the car estimates your oil is degraded or `exhausted’ – then at switch-on your flight deck will display (something like) [exhaust oil]. (See Owner Handbook).
Diesel engines running uncontrollably.
Honest John/Telegraph 2009.11.21
Mazda sicks
I bought my 2006 Mazda6 2.0 diesel in November 2007. On the M74, the engine revved uncontrollably and I noticed a lot of smoke coming from the rear. I managed to get the car to the hard shoulder and eventually managed to switch the engine off.
After a few minutes I started the vehicle but again the engine revved uncontrollably. After waiting 10 minutes I was able to drive off - only to notice the DPF light was on, then later it started to flash and the engine management light came on.
My Mazda dealer told me it only needed an oil and filter change. I explained what had happened on the motorway and they said was that it was probably due to the high oil level and oil filter. They checked the car but found nothing wrong, changed the oil filter and oil and reset the computer.
I have had the car in many times since, all relating to the DPF, smoke and high oil level.
M.C., via e-mail
The DPF is both passive and active. In passive mode it burns off particulates through heat generated by the engine and exhaust system, so will do this on fairly long motorway journeys at 2,000rpm-plus.
It also has an active function, where extra diesel is injected into the combustion chambers to create enough heat to burn off the particulates as it is exhausted.
If it doesn’t burn completely, the excess diesel sinks into the engine sump where it contaminates the lubricating oil and raises the level.
Since diesels are compression-ignition engines, once this level gets too high they will start running on their own lube oil and can only be stopped by stalling them or by stuffing the air intake with rags (which few people are willing to do against a raging engine).
Mazda strongly advises in the owner’s handbook to check the oil level regularly, and if it rises to the ‘X’ mark get your car to the dealer for a check and an oil change.
It’s a common problem with the Mazda6 2.0 diesels with DPFs, with Subaru Legacy diesels, with Fiat 1.3 Multijets in 500s and Vauxhall Corsas, and increasingly with Peugeot and Citroen 2.0HDI 16v engines.
Source:
http://www.telegraph.co.uk/motoring...65/Diesel-engines-revving-uncontrollably.html
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Nuova Croma 1.9/16v 150hp