The first he knew of it was when a message flashed up on the Insignia’s dashboard saying the filter had been unable to regenerate itself. A few seconds later, the car went into limp home mode. The Vauxhall dealer McCabe spoke to said that if the DPF was damaged and his ‘driving style’ was to blame, he’d be liable for the repair bill – a not insignificant £2500 plus £960 fitting.
“It seems that the manufacturers have the right to decide whether the failure of the DPF is a warranty issue or not, based on your ‘driving style’,” said an aggrieved McCabe. Fortunately for him, the Insignia’s DPF was simply faulty and was replaced at no charge. McCabe was relieved but not entirely happy. “It’s obvious that on certain used cars, the DPF will cost more to replace than the vehicle itself is worth,” he wrote.
His experience triggered a few tales from Autocar readers who had suffered DPF issues with their cars. They included Julian Fack, owner of a Porsche Macan S Diesel that, since he bought it, has signalled problems with its DPF on four occasions – roughly every 6000 miles. On two of them, it went into limp home mode and required a dealer to carry out a forced regen.
“There can be as little as a minute between the car alerting you to a problem and it going into limp home mode,” says Fack. “In that time, and assuming you’re on a clear road, you must start the regen process, which involves driving the car at no less than 37mph for 10 minutes with the engine turning at over 2000rpm.”
Another reader, Nick Wilson, explained how he’d bought a new Land Rover Discovery Sport in March 2017, only to sell it 18 months and 37,000 miles later after it developed an appetite for more frequent oil changes. “The dealer suggested short journeys and my ‘driving style’ were to blame but I travel all over the country so the car gets a good workout,” says Wilson.
He later discovered the problems had less to do with his driving style and more to do with an oil dilution issue common to some 2016-17 model-year Range Rovers, Discoverys and Evoques.
A bulletin sent to Land Rover dealers and headed ‘Early service due to oil dilution’ explains that the ‘service required’ message is triggered by unburned fuel in the engine oil, itself caused by a higher-than-expected number of partial DPF regeneration cycles.