Everyone knows a diesel car is more efficient than an equivalent petrol car.

Depends on various factors, making a simple, one-size-fits-all answer impossible.

Let Overview

However, I can provide you with information to help you To decide

Which might be the most cost-effective choice for your specific situation

Initial Cost

Petrol  Generally the cheapest upfront purchase price. Diesel  Slightly more expensive than petrol initially. Electric Most expensive upfront due to battery technology costs.

Running Costs

Petrol  Most expensive per mile due to higher fuel prices. Diesel  More fuel-efficient than petrol, leading to lower per-mile costs. Electric Very low running cost per mile due to electricity being cheaper than fuel. However, factor in charging costs and potential range limitations.

Other Considerations

Government incentives   Some regions offer tax breaks or rebates for electric vehicles.  Maintenance  Electric vehicles generally require less maintenance than petrol or diesel cars.   Environmental impact  Electric vehicles produce zero tailpipe emissions, while petrol and diesel contribute to air pollution.    

Driving habits : If you primarily take short trips, an electric vehicle might be ideal. For longer journeys, diesel or petrol might be more practical currently.