It emerged last week that Essex Police force has resorted to fitting verbal warning systems to prevent drivers filling cars with the wrong fuel.
The force has shelled out for 222 separate misfuelling incidents over the past five years, at a total repair cost of £42,000.
To combat this, fleet administrators fitted bright yellow flaps over the tank entrance and automatic voice reminders that prompted: “This is a diesel.”
The misfuelling systems have been fitted over the last couple of years and cost between £5 and £10 a vehicle.
A police spokesman said: “Essex Police, like many other organisations, has previously suffered from wrong fuels being put into tanks. Part of the problem is that modern diesels are so good and quiet that drivers can be easily fooled into thinking that they run on petrol.
“Police officers and staff often drive a variety of vehicles during the course of the week and they may be either petrol- or diesel-fuelled.”
The force said that not all of the vehicles in its fleet of 900 were fitted with the system.