Ask the expert: My Volvo is indicating it has too much oil – what is happening? – Telegraph.co.uk

Alex Robbins is contributing editor at Telegraph Cars where, as well as responding to readers’ queries, he also contributes reviews of new and used cars, together with articles on buying and selling. 

His knowledge of the used car market informs his many buying guides relating to the best buys in particular sectors, with an emphasis on value for money.  Every week he will answer your questions on buying and selling, as well as solving your car problems, whether consumer or mechanical.

Do you have a motoring dilemma you’d like our expert to solve?  For consumer and used car advice, or car faults, email CarsAdvice@telegraph.co.uk and include your subscriber number. This week’s question… 

Dear Alex, 

I own a 2017 Volvo XC60 diesel with 25,000 miles. Over the last few weeks the system check is advising that the engine is overfilled with lubricant, despite none having been added. My Volvo dealer said it is aware of an issue of this sort and that it is connected to catalytic converter regeneration. They suggested that I have the oil changed and re-filled to the correct level, to which I agreed. As an ex-fleet engineer, I am suspicious since in my experience the usual reason for a too-high oil level was fuel return lines diluting the lubricant in the sump, although I am sure that this is not the case here. What do you think? 

– GW

Dear GW,

Do you do lots of town driving, and not much on the motorway? If so, my first impressions are that the dealer’s assessment is correct. It could indeed be that your diesel particulate filter (DPF) is clogged. The DPF’s normal regeneration cycle requires the exhaust to be hot, which is why it normally takes place on a motorway. 

If the exhaust isn’t hot enough and a regeneration cycle needs to take place, the system will pump more fuel into the engine to get it up to temperature quickly. If the filter is well and truly blocked, the regeneration can fail and the excess fuel can find its way back into the engine via the exhaust gas recirculation (EGR) system and end up in the sump. Or if the car is switched off, interrupting a regeneration cycle, the fuel can end up in the oil system by seeping down the cylinder bores. 

If this is the problem, you should change the oil and filter anyway, because it will be contaminated with fuel, so the dealer’s fix is right. And to prevent it from happening again, you’ll need to do some long motorway runs, enabling the exhaust system to get up to temperature, which will hopefully allow a few regeneration cycles to unblock the filter. 

Having said all of that, a bit of digging around in the Volvo owners’ community reveals several other owners of new-ish Volvos have had this message too, but for a very different reason. It seems the system that measures the oil level has a very low tolerance for incorrect levels, and if it isn’t calibrated correctly it can throw up erroneous error messages. In your case, the dealership may only need to re-calibrate the oil level sensor, though it might also need to update its software too. I’d suggest trying this first. 

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