Most of us have an inkling of how basic forms of car technology works. Most of us know that cars are powered by an engine and we know that these engines need fuel to work.

For a lot of people, that’s as far as their mechanical knowledge of how those wheels turn actually goes though. And understanding a fundamental aspect of your car’s technology, like the engine, is really important for helping you choose the right lease car.

So, how do those intricate, mystical machines inside the bonnet (or at the rear of your car) actually work?

I’ve made this set of pages to help you. This section should hopefully give you a basic grounding in how engines work, what types of car engines exist and what types of fuels they use. I’ve also included some of the best types of cars available for each type of fuel. Happy reading!

The Internal Combustion Engine

To start with, let’s go back to basics.  

The most important part of a car is obviously its engine which provides the power to move it forward. The engine that’s predominantly used in cars is called the internal combustion engine. There are two different types of these engines: the spark ignition and the compression ignition internal combustion engine.

Spark ignition internal combustion engines

This is probably the most common type of internal combustion engine that’s found in cars throughout the world. It’s fuelled by petrol.

A spark internal combustion engine is made up of a series of hollow cylinders, which each have a spark plug, an exhaust port, and a piston in-cased inside. These pistons are connected to the crankshaft, the drivetrain and the wheels.

When in operation, petrol is mixed with fuel before entering the cylinder and is compressed slightly by the piston. The spark plug then ignites the petrol and air mixture, with the mini explosion and high-pressure gas created by the combustion process forcing the piston to move. This in turn, rotates the camshaft, moves the drivetrains and rotates the wheels, causing the car to move. The piston will then clear the spent gases from the cylinder and the process will repeat.

Compression ignition internal combustion engines

This type of internal combustion engine is powered by diesel. The structure of the engine is the same as the spark ignition internal combustion engine, but there isn’t any spark plugs.

Air is allowed into the cylinder and then highly compressed by the piston, significantly raising the temperature of the air. Fuel is then injected into the cylinder and instantly ignites, forcing the piston to move and turn the crankshaft.


An internal combustion engine doesn’t run on thin air unfortunately – you need something to power it. That’s where fuel comes in.

Internal combustion engines, and similar car engines, are overwhelmingly powered by two fossil fuels at the moment: petrol and diesel.

Petrol and diesel is derived from petroleum, a liquid/rock deposit that was formed over millions of years by the fossilisation of dead animals and plants. That’s how petroleum gets its name as a ‘fossil fuel’. Petroleum also gives a range of other fuels like kerosene, propane/propylene and still gas.  

Fossil fuels provide good power overall but have a major problem in that they are damaging the environment, significantly contributing to global warming and climate change.

Answering that age old question: petrol or diesel?

We’re going to be honest and say that there’s benefits and negatives to each and what might be good for one person, might not necessarily be right for another. We’ve covered the arguments for and against each in this section, to help you decide between petrol or diesel. If you’re strapped for time, here’s a summary though:


A form of distilled, and then refined, petroleum, petrol is probably the most widely-used fossil fuel across the world. It powers everything from lawnmowers and electric generators to luxury cars.

Petrol’s main benefit over diesel is that it’s cheaper at the pump. That said, it doesn’t provide the same levels of fuel efficiency as diesel so you’ll probably have to fill up your tank more often – costing you more in the long term. It still produces emissions and pollution too, which is having an effect on the health of our climate, and it’s finite – petroleum deposits will run out in about 53 years, based on our current rates of extraction.


Like petrol, diesel comes from petroleum. It isn’t distilled and refined to the extent that petrol is, giving it more energy and power. Thanks to the fact that the fuel is compressed in an internal combustion engine, and not ignited, diesel engines are about 20% more efficient than petrol-powered, spark ignition ones (you can read more about this below).

The major negative to diesel duel is that it’s much dirtier when it burns, giving off more noxious emissions than petrol and significantly damaging the health of people and the environment. It’s also finite, so, like petrol, it will run out one day soon.

Electric power

The main alternative to petrol and diesel is electric power, which has steadily been developing in capability in recent years. The diesel scandal has further increased demand for non-fossil fuel forms of power too.

How an electric car works

So, how does it work?

In an electric car, electrical energy is stored inside the chemicals of a battery (usually a lithium ion battery).

When the car is switched on, an electrical current is produced from the battery which sends electricity to the car’s motor. Electricity flowing through this motor creates a force called electromagnetism.

The motor itself made up of a number of magnets arranged in a circle around another magnet in the centre, which is directly connected to the wheels of the car. Electricity can be directed to these outer magnets in sequence, generating what’s known as an alternating current. The attraction and repulsion force that’s generated between the outer magnets causes the central magnet to move, in turn driving the wheels and giving you movement.

The fact that the wheels are directly connected to the motor allows much higher levels of torque and energy efficiency than you’d find in an internal combustion engine.

Electric power benefits from being completely emissions-free, and it has the potential to be generated by renewable sources, possibly making it a completely sustainable form of energy in the future– unlike petrol and diesel. The major drawback to electric cars at the moment is the fact that they have a limited distance that they can travel before needing to be recharged – usually between 50 and 300 miles. They also require pretty large batteries (check out the killer battery on the Tesla Model S for an example).

There’s loads of different types of electric vehicles to choose from with car leasing, to suit the budgets of most people – whether you’re after luxury electric cars or family electric cars, the best electric cars that money can buy or the cheapest electric cars that are currently available.

Finding out what car manufacturers make electric cars isn’t as difficult as it once was because most now offer some form of electric-powered vehicle in their ranges.


Electric cars are further split into different types. One of these sub-groups is known as the hybrids. These are essentially petrol or diesel cars that are capable of using electric power fully, or partially.

Most manufacturers make hybrid cars these days, and there’s loads to choose from: luxury hybrid cars to hybrid crossovers to hybrid SUVs.

You can get the best hybrid car, the most efficient, or you can get the cheapest hybrid car. There’s definitely enough choice out there.

Parallel hybrids

Parallel hybrids usually give you three options of power. Full electric, full petrol/diesel or a combination of the two. They’re probably one of the most versatile types of hybrids around.

Series hybrids

Series hybrids are mainly powered by an electric motor, but this can get additional support from a petrol/diesel generator.

Mild hybrids

Mild hybrids aren’t strong enough to power the car using electricity alone, so the battery instead provides additional support to the main internal combustion engine.

Plug-in hybrids (PHEV)

Plug-in hybrids (abbreviated to PHEV) can be charged directly, allowing you to drive considerably longer distances than a conventional hybrid.

Alternative fuels

Alternative fuels to petrol, diesel and electric are being developed too. Here’s some details about some of the key ones for you.

  • Biofuel: Extracted from plants, biofuels are what’s known as a carbon-neutral fuel source. This means that the carbon dioxide they give off when they’re burnt is balanced by the carbon dioxide that they absorb when they’re growing. Biofuels can be used independently to power particular types of engines or they can be mixed with diesel to create biodiesel.
  • Hydrogen: Hydrogen is one of the world’s most common elements so it makes sense to try to harness its power somehow. Scientists have managed to do that to a degree with the hydrogen fuel cell.
  • Ethanol: You know what ethanol is already – it’s alcohol! Derived from plants, ethanol is similar to biofuel in that it can be blend with other fuels to power cars.

All Ultimate Guide to Car Engines and Fuel Technology Blogs


Petrol vs Diesel: Which Is The Better Fuel?

Petrol and diesel are the two main fuels that we use to power our cars. Both have their obvious pros and cons, but which one should you choose if you’ve about to start leasing a car?

01 Oct 2018 10:11am
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What Is A Hybrid Car? And Should I Buy One?

Hybrid is a word with a lot of scary associations – usually to do with mutants – so it’s good to pin down what it actually means. It just means a combination of two different elements. In the case of cars, a hybrid is a vehicle that combines petrol or diesel power with electric power.

17 Jul 2018 8:24am
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Is Petrol or Diesel Cheaper?

Petrol and diesel are the two main fuels that we use to power our cars. Both have their obvious pros and cons, but which one should you choose if you’ve about to start leasing a car? I’ve created a small guide with the pros and cons of petrol and diesel to help you decide.

17 Jul 2018 8:24am
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