Why Do UK Police Cars Keep Exploding?

Detailed explanation of the Ex-Police Car Auctions:
   • The Clocked Up Holy Engine Scandal of...  

Nick Dumphreys was a policeman who was part of the Cumbria constabulary, where his wife, Kathryn, also worked.

In January of 2020, Nick was heading down the M6 in a BMW 330d, responding to a 999 call.
Given the nature of the call being a pretty serious assault with weapons involved, getting there quickly was of utmost importance.
Nick brought the car up to a speed of roughly 130 miles per hour.
As he accelerated, the BMW's engine effectively ate itself. just after he'd passed junction 44.
A faulty crankshaft bearing had broken loose, which punctured the oil sump. Nick's car spat most of it's oil out onto the road, which ultimately is what caused his life to be tragically cut short.
Nick lost traction from the oil going everywhere - the car swerved off
the edge of the motorway, flipped over and caught on fire. A later inquest
determined there was 'nothing he could do' to have prevented this.

Now although initially it might not have seemed like Nick's unfortunate demise had anything else to it, an inquest was opened after the event, which uncovered some less that favourable truths about the whole situation, and potential oversight to the safety of police officers as a whole.

This wasn't the first, or last, event like this to have occurred. In fact, the inquest had shown similar faults had been reported between 5 and seven times per month between 2014 and 2017.
These issues are specifically referring to BMW Police cars with the N57 diesel engine. The N57 is fitted in a number of different BMW models the police commonly use here, mainly the 330d touring, 530d touring, and x5.

You might be wondering why it's almost only police cars which have encountered this pretty catastrophic issue, and the reason for this is mainly down to how the cars are driven.
BMW put out a statement following this all coming to light, saying this:

“‘This issue is associated with the particular way in which the police operate these high-performance vehicles.
This unique usage profile puts extra strain on some components and therefore BMW has specified a special servicing program
for these vehicles,’. ‘There is no need for action on any civilian vehicles’.

It seems that the nature of the usage they are talking about is idling for long periods of time, moving and a snails pace and then immediately
thrashing the cars. Since a car could be taken from cold up to 100 miles per hour, before idling for an hour and them immediately thrashed again right afterwards, it's not the easiest life these cars go through.

BMW Engineers in Austria went about testing seven engines, and discovered the main culprit of these fires is down to poor lubrication, caused by ageing engine oil.

There's a bit of confusion when you dive deeper into the Police's routine issues with 3.0 litre diesel BMWs.
Before the N57, came the M57. Both engines are 3 litre inline sixes, and the Police have used cars fitted with both engines in the past.

Depending on the reports you read, both the N57 and M57 are brought up as having fire issues.

The BBC reports that the N57 had been failing 5 to 7 times per month, whereas the Manchester evening news say it's the M57.

Interestingly, in early 2022, the police began winding down their use of the cars for higher speed usage. Across the nation, police officers were told to keep it below 90mph as an absolute maximum, regardless of circumstances. Not only that, but a number of specific forces withdrew the cars from use altogether, including Hertfordshire, Northumbria and
Cumbria, the force Nick belonged to.

Following on from the winding down of BMWs by the police, and presumably a lot of back and forth arguments
behind closed doors, BMW announced it was no longer going to supply the police with cars earlier this year,
which can ultimately be traced back to Officer Nick's unfortunate demise in 2020.

So, with a whole load of M57 and N57-engined cars no longer of any use, what did the police decide to do with them?
Well, just like many other ex police vehicles, a lot of them have ended up in police auctions, although with a bit of a twist.
They've been drilling holes in the side of the engine block, to effectively render the cars as useless.
The main reason they justify doing this is "public safety", since the cars are at a raised risk of catching fire.
But fundamentally, as long as the Diesel particulate filter gets cleared out fine and the car isn't used like a police car, this shouldn't be an issue. What we're then left with is a huge waste of money, and it certainly isn't good for taxpayers or the environment.
But there we go, that's the quickest solution they could think of.