Is a diesel cheaper to run than a petrol? Yes, diesel engines typically use 20%-25% less fuel than their petrol equivalents. With fuel priced similarly, diesel cars can be a better buy. Does diesel use less fuel? Due to continuous improvements in technology, the diesel engine continues to be more fuel efficient than similar-sized petrol engines. While a petrol engine combusts a mix of air and fuel ignited with a spark, diesel engines only compress air, then inject fuel which ignites automatically. The high compression pressure and temperature mean that the fuel can ignite without the need of a spark. As a consequence, a diesel engine uses more air and less fuel, making them more fuel efficient than spark-ignited petrol engines. Fuel consumption is also influenced by horsepower. The more horsepower an engine has, the higher the fuel consumption. While diesels tend to have more torque, the horsepower is lower because of the lower revolutions per minute (RPM). Diesel engines are therefore able to consume less fuel while delivering the same power as their gasoline alternatives. This is why a diesel car can typically run for much longer than a petrol car in-between refuelling. Are diesel cars better for long-distance drivers? Diesel’s fuel economy is superior to similar-sized petrol engines, as diesel cars consume less fuel per unit of distance. This makes them the ideal choice for long-distance driving. Fuel consumption is also influenced by the fuel itself: diesel fuel contains roughly 15% more energy than petrol because it is denser. Accounting for the energy density difference, the overall efficiency of the diesel engine is about 20% greater than the petrol engine. Consequently, diesel is the most suitable choice for long-distance driving. The diesel engine’s higher fuel efficiency makes diesels cheaper to run overall, and it also impacts the resale value of the vehicle. Studies show that even though diesel cars often have a higher monthly lease cost compared to petrols, their fuel efficiency reduces fuel costs. This is particularly relevant for high mileage drivers. Diesel fuel costs are also generally lower in most European countries. Diesel engines are consuming less fuel while delivering the same power as their gasoline alternatives. Coupled with a better fuel efficiency, the lower fuel cost for diesel cars usually offsets the higher lease costs, with diesels being better suited to long-distance driving and offering greater fuel economy. When is it better to buy a diesel? To conclude, different cars correspond to different needs and using the right powertrain is essential for consumer satisfaction. For drivers who use their vehicle for long journeys, thanks to the higher fuel concentration and efficiency, diesel remains the best possible choice. Consumers should therefore make their decision based on their own needs. Due to their advanced fuel economy and efficiency, diesel cars are cheaper to run than petrol. They also have greater return values especially for larger vehicles. Lastly, their fuel contains more energy and that makes them the ideal choice for long-distance driving.Is a diesel cheaper to run than a petrol?