Keep on running

▶ I’ve had this conversation a couple of times lately, so it may be worth repeating here. As we are all hopefully aware, modern diesels have DPFS (diesel particular filters). These are big canisters in the exhaust, which collect soot rather like a bin bag collecting rubbish.

This rubbish is then disposed of via a bonfire, aka the ‘regen’ process inside the DPF. It is usually ignited by diesel injected on the exhaust stroke or, ideally, by the heat generated by a long, fast drive. This can only happen when the coolant and oil temperatures are up to the required level, with plenty of fuel in the tank, and when the engine is under a constant load. Motorway driving then.

If you’re not often on a motorway, then there will be a forced regen by the car using lots of diesel to get the bonfire underway. This isn’t good because, if you slow down or switch off, all that fuel thrown into the cylinders to start the bonfire is washed down the piston bores and into the engine oil sump, shortening oil life and overfilling the sump.

This is the where I’ve seen confusion this week. Adblue is there to further chemically clean the exhaust emissions after the DPF. What it cannot do is make up for a lack of motorway driving, or too much urban or stop-start driving.

It is not there to help the DPF or make allowances for your driving style.

Take the Skoda Octavia Scout that

I got into the other day. For months it had only been used for short runs and had been furiously trying to regen around town in-between shopping trips (the cooling fan running on after switchoff is the audible giveaway, and one that destroys batteries). The sump was overfilled, the oil life reduced to nothing.

After its service I took it out and onto the motorway. A forced regen using plugin software outside the workshop was an option, but this should only be the last resort. Instead, I took it on a run down the motorway and used the car for the