Rising oil level

Q I own a 2011 Vauxhall Astra 1.7 CDTI that has a problem with a constantly rising oil level. This only occurs during the winter or cooler weather. The level rises from the midway point on the dipstick to above maximum in around 2000 miles, which only takes about seven weeks as I do 15,000 miles annually. This leaves me having to perform expensive early oil changes, as I don’t like the idea of diluted oil being in the engine.

After researching online, I have drawn the conclusion that it is likely to be due to failed regeneration of the DPF. I use the vehicle for 90% motorway journeys and assumed that this would be sufficient to keep the

DPF in good health. Is there anything I can do to prevent it from occurring?

Is it likely to affect all Dpf-equipped diesels for the type of driving I do? If so, I am seriously considering selling the car and returning to petrol power. Steve Lee

A The type of driving you do is actually ideal for maintaining a DPF, giving it plenty of opportunity to successfully regenerate. It is possible that the system may need a software upgrade or that there is a failed sensor in the system.

The rising oil level in your vehicle is excessive if it’s being caused purely by failed regenerations. You do not mention the mileage of the vehicle, but the problem may be due to a weeping injector allowing excess fuel into the engine. If this was the case, I would also expect higher-than-normal fuel consumption, coupled with an uneven tickover.

Another possibility is that, as the injectors are housed within the cam cover, there may be a leak from the injection system within the cam cover which is allowing the diesel to travel straight into the sump. If this is the case, it’s possible that no outward signs would be visible.

You were wise to change the oil, as the degrading of the oil from the addition of diesel will affect the lubrication of the engine components.