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Petrol vs Diesel – The most fuel-efficient option

Diesel cars are generally more fuel efficient than their equivalent petrol counterparts, in certain cases up to 31% according to the manufacturers’ claimed figures.

The reason for this is that diesel has approximately 10% to 15% higher energy density than petrol and therefore a higher compression ratio, a more efficient combustion process, and lower fuel usage, according to the European Automobile Manufacturers’ Association.

There are, however, drawbacks to the less refined propellant.

Mainly, diesel motors tend to be heavier than petrol engines as well as more expensive to produce.

Because of the higher compression ratio and mass, these oil burners also generate more torque than horsepower, which can lead to slower acceleration.

Diesel engines generally produce more smoke and are noisier, too, and they must be fuel injected which in older models was expensive and less reliable.

Moreover, since petrol engines have more power while electric motors have more torque, diesel units do not complement hybrid powertrains as well as petrol does.

These caveats have caused many automakers to start moving away from the technology in the march to a new-energy future except for those of larger bakkies and SUVs, as well as the odd sedan and crossover.

Petrol vs Diesel

Compared in the below tables are the fuel consumptions, power figures, and prices of eight popular vehicles which are available in both petrol and diesel guises.

In the worst-case scenario, the diesel model only improved upon the fuel usage of the petrol model by 6%, and at best, it went up to 31%.

Moreover, all eight diesel specifications boasted from 9% to 117% more torque than their petrol equivalents, and in seven out of the eight examples, the diesel was between 4% and 34% more expensive than the petrol.

Click on the underlined prices for more information.

Audi A5

Specification 40TFSI 40TDI Diff.
Fuel consumption 6.4l/100km 6.0l/100km -6%
Power 140kW 140kW 0%
Torque 320Nm 400Nm +25%
Starting price R849,000 R944,700 +11%


Specification sDrive20i xDrive20d Diff.
Fuel consumption 7.3l/100km 5.6l/100km -23%
Power 135kW 140kW +4%
Torque 300Nm 400Nm +33%
Starting price R1,015,778 R1,065,394 +5%

Ford EcoSport

Specification 1.5 1.5TDCi Diff.
Fuel consumption 6.4l/100km 4.6l/100km -28%
Power 91kW 74kW -19%
Torque 150Nm 205Nm +37%
Starting price R311,400 R322,500 +4%

Hyundai Tucson

Specification 2.0 2.0D Diff.
Fuel consumption 8.9l/100km 7.4l/100km -17%
Power 115kW 137kW +19%
Torque 192Nm 416Nm +117%
Starting price R572,900 R764,900 +34%

Kia Seltos

Specification 1.6 1.5CRDi Diff.
Fuel consumption 6.9l/100km 5.1l/100km -26%
Power 90kW 86kW -4%
Torque 151Nm 250Nm +66%
Starting price R440,995 R470,995 +7%

Mazda CX-5

Specification 2.5 2.2DE Diff.
Fuel consumption 7.3l/100km 5.7l/100km -22%
Power 143kW 140kW -2%
Torque 258Nm 450Nm +74%
Starting price R729,500 R765,300 +5%

Mercedes-Benz C-Class

Specification C200 C220d Diff.
Fuel consumption 6.8l/100km 4.7l/100km -31%
Power 150kW 147kW -2%
Torque 300Nm 440Nm +47%
Starting price R1,007,056 R1,072,599 +7%

VW Tiguan

Specification 2.0TSI 2.0TDI Diff.
Fuel consumption 8.3l/100km 6.6l/100km -20%
Power 162kW 130kW -20%
Torque 350Nm 380Nm +9%
Starting price R819,800 R818,600 -0.15%

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