Pros and Cons of Diesel and Petrol Cars

Buying a car is a major step, especially if you consider the purchase price, maintenance and the fuel cost. It pays to do the research, so you can make the right decision.

In Europe 50% of new cars have diesel engines, while in the USA the number is 3%. This is partially because of tighter emission standards in the USA. It does however look as if the diesel engine share in the USA is growing, probably partially because of improvements in diesel engine emissions.


Petrol is more universally available than diesel. You should probably check diesel availability in your area before buying a diesel car. Some areas in smaller countries have been known to run out of diesel completely, when there are supply problems.


Diesel engines tend to last longer than petrol ones. Not only does that mean you can drive a diesel car longer, but if you decide to sell it, the resale price will be higher.

Relative price

In terms of price per litre, diesel is slightly more expensive than petrol in the larger markets, but you can go further on a litre of diesel (diesel is between 25 and 30% more fuel efficient). Because diesel is also used to heat homes the price may go up during winter. In some smaller countries diesel is cheaper than petrol.

Check the current UK prices

Next we look at 3 problems with diesel engines that have been largely overcome with new technologies, during the last decade. If however you buy an older diesel car, there may still be issues, with these diesel engine cons.

  1. Greater noise and vibration than with petrol engines.
  2. Smoke and a strong smell from the engine.
  3. Problems starting a diesel car, when it's cold. Diesel vehicles that use glow plugs needed to warm up the plugs before you could start the car.
  4. Diesel fuel didn't use to be very clean. Some engines have water separators to clean the fuel, these may need to be emptied manually.

Diesel engine

Diesel engine

There has been a lot of pressure from governments to reduce vehicle emissions, in recent years. Both types of cars have benefited from advances in technologies, but diesel car engines have benefited more.

Maintenance cost

Diesel engines have no distributors or spark plugs, so they don't need to be changed or maintained. You still need to change the oil and the filters in the car. These engines are more advanced, so if you do neglect them and they need to be repaired it can cost more than with a petrol car.

Power and Torque

Petrol engines have more power, while diesel ones have more torque. Say you are opening a jar, the twist you apply to the lid before it starts to move, that is torque. When it starts to move, to spin it faster you apply power. So what that means is with a diesel engine you can really feel the torque when you start moving from a stopped position.

If you want to compensate for the lack of power, look at turbocharged models.


The upside of using biofuel is that it significantly reduces the amount of carbon released into the atmosphere. The downside is that arable land is used to create fuel and not food. Doing so increases the cost of food.

Petrol biofuel

Bioethanol is made by fermenting sugarcane or corn. This is then added to petrol to reduce the net carbon emissions from petrol engines.


Biodiesel is made from the transesterification of oils and fats. Most diesel engines can run on pure biodiesel, but it's more likely to be added to regular diesel.

Biodiesel use is more popular in Europe, while bioethanol is more widely used in North and South America.


The bottom line

What it comes down to, for most people, is the overall lifetime cost of operating a vehicle. Diesel cars are more fuel efficient, but have a higher initial price tag, so the question becomes: How much are you going to drive the car? With a work car it's a no-brainer, but with a personal vehicle you need to sit down and look at the cost and fuel efficiencies of the options that you are considering.




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