There have been more than 2,100 cases of police officers putting the wrong fuel in cars since 2011, according to an investigation by Auto Express.
It found police forces in the UK have spent nearly £400,000 in the last five years on repairing their fleets after officers filled patrol cars with the wrong fuel.
Since 2011, there have been 2,147 incidents of an officer putting the wrong fuel in their vehicle while on duty – more than one every day.
The error has cost forces a collective £390,061 to repair misfuelled vehicles – at an average of £181.68 each time. Forces spent a total of £378m on fuel in the last five years, meaning £1 is spent on repairing a misfuelled vehicle for every £970 spent on diesel or petrol.
The force with the biggest repair bill was the Metropolitan Police, although it also spent the most on fuel (£64.6m). Taking fuel spend into account, Warwickshire is the worst offender, spending £1 on repairs for every £331.99 on fuel.
Some forces had no misfuelling errors, however. Greater Manchester Police and the Police Service in Northern Ireland have bunkered fuel sites with pre-programmed keys to ensure the correct type of fuel is dispensed.