Aside from whether it’s petrol or diesel, most drivers don’t think about the fuel they put in their car. But as new technologies continue to emerge and the need for more economical engines grows, motorists are seeing a greater number of pumps at the petrol station – from Super Unleaded to LPG Autogas.

The question is, what sets these new fuels apart from traditional petrol and diesel? In this guide, we explore how different car fuels are produced and the cars and engine types they’re best suited to. We’ve also included a section on looking after your car’s fuel system, so you can ensure optimum engine health and performance.

Use the links below to jump to the fuel you’re interested in, or read on to get stuck into the complete guide.

  1. Petrol and Diesel
  2. LPG Autogas
  3. Biofuels

How Fuels are Produced

Petrol and Diesel

Since the invention of the combustion engine, petrol and diesel fuels have been used to power our vehicles. But where exactly do they come from, and how are they produced?

Both petrol and diesel fuels come from crude oil, which is sourced from vast oil fields within the Earth’s surface. On its own, crude oil isn’t suitable for use in engines – it doesn’t have the explosive properties needed to power the cylinders. This is where the refining process comes in. Under high temperatures the oil separates into different types of fuel, including petrol, diesel, jet fuel and heavy oil (which is commonly used in tarmac).

oil pumps

When crude oil is heated in a refinery tank, petrol and diesel vapours rise to the top and condense. This liquid is siphoned off through oil pipelines, before being transported to fuel stations across the country for use in cars, trucks and other vehicles. Diesel and petrol fuels differ because diesel requires less refinement and less crude oil to produce than petrol. However, due to tighter regulations on ‘clean’ diesels, the refinement process for diesel fuels is changing – and with it the cost of fuelling your car.

Generally speaking, diesel is considered more economical than petrol for people who cover a lot of miles on faster roads, such as motorways and A roads. That’s because, in chemistry terms at least, it’s around 15% more ‘energy dense’ than petrol, meaning that the engine can extract more power from every litre of the fuel.

LPG Autogas

An emerging fuel which is steadily gaining popularity, LPG Autogas is a common name for Liquefied Petroleum Gas, a mix of propane and butane that are by-products of the oil refinement process. According to LPG fans, DriveLPG, there are now around 170,000 cars on the road which run on LPG, with over 1,300 fuel stations offering it, particularly in urban areas.

LPG Autogas

LPG is made during the oil refinement process, when crude oil is heated in a distillation tower and its vapours condensed. LPG can be used in its liquid state or separated into butane, propane and isobutene. These are commonly used in machinery, electricity generation, or bottled and used as fuel for camping stoves and barbecues.

One of the benefits of LPG Autogas is that when it’s burned in an engine, it produces much less CO2 than petrol and diesel – so much so that cars running on it are exempt from city congestion laws and charges. However, it’s nowhere near as economical as petrol or diesel, with an average MPG range far below that of the equivalent tank of petrol or diesel.


Although nowhere near as advanced or widely-used as fossil fuels such as petrol and diesel, biofuels are considered much more eco-friendly and sustainable, as they don’t rely on the distillation and refinement of crude oil – a process which accounts for a huge proportion of the world’s CO2 emissions.

Biofuels such as bioethanol and biodiesel are derived from biomass – waste materials from plants that can be used as a type of fuel. Biofuels normally contain a mixture of bacteria, methanol and yeast which form during fermentation. This mixture is blended with petrol and diesel to produce an effective and stable fuel source, and today, most petrol and diesel products contain a percentage of biofuel, helping to make them more efficient and environmentally sound.

When they were first introduced, biofuels made up around 1% of the petrol or diesel fuel mix. Since then, this figure has risen to 3.5%, with the quantity of biofuel added expected to rise to 5% in the coming years.

Biofuels aren’t only used as a green additive in petrol and diesel; they can power a vehicle on their own depending on how the car is set up and modified. Some manufacturers now offer a 50/50 mix of petrol/diesel and biofuel, as well as 100% biofuel products which are designed to power purpose-built green petrol and diesel engines.


While biofuels are currently only an additive, it’s expected that they’ll become more and more popular in the years to come, as car manufacturers look to continue reducing emissions and improving efficiency.

Fuel Types and Cars

Certain fuels are better suited to some engines and car types than others, offering benefits in specific situations and for different driving needs. Here, we look at the types of cars and driving environments that are better suited to the main fuel groups.


Cars: From the hatchback to the saloon, petrol is used in many cars, particularly those built for affordability rather than performance. Petrol engines aren’t nearly as complex as diesel ones, as they don’t require a massive amount of compression, so petrol is a common fuel in inexpensive family cars, hatchbacks and small, eco-focused city cars.

Driving Situations: Offering a good mix of performance and economy in town and on the road, petrol is a great all-round performer. However, it’s not quite as economical as diesel, so it’s not recommended for motorway mile-munching.


Cars: Diesel fuels produce lots of engine torque, making them great for high-performance saloons, 4X4s and large, heavy commercial vehicles such as vans and trucks. Because more technology is needed to harness the power of the fuel, diesel cars tend to be more expensive and high-end than the petrol equivalent (although some smaller hatchbacks, including the Vauxhall Corsa and Ford Fiesta, have a diesel variant).

fuel pumps

Driving Situations: Diesel engines come into their own on faster roads, where their performance offers great fuel economy and overtaking ability. In town, however, modern diesel engines can suffer from blocked DPF filters. Learn more about DPF filters here.

LPG Autogas

Cars: Small cars, such as hatchbacks and city cars, are generally better suited to LPG Autogas. That’s because they use less fuel than more powerful, high-capacity engines.

Driving Situations: LPG is great for those who live in town and do minimal miles in the car. That’s because the poor economy figures are offset by the savings made on the cost of the fuel itself.


Cars: Currently, biofuels aren’t used in any specific type of car, but are added to petrol and diesel products to make them more eco-friendly. However, some manufacturers, including Audi and Ford, have started developing cars which run purely on biofuels, and these are expected to afford a decent ratio of economy and fuel efficiency.

Driving Situations: It’s not yet clear where biofuels will offer benefits for drivers, whether in town or on the motorway. However, solid fuel efficiency figures will mean they’re an excellent choice for those who regularly drive in areas that have a congestion charge.

Caring for Your Car’s Engine with Redex

Redex fuel additives are developed for petrol and diesel engines, and allow for improved performance and better engine health. Below, we’ve listed the products we’d recommend for caring for your petrol or diesel engine.



If you regularly top up your car with standard unleaded fuel, here are the Redex products we’d recommend to improve your car’s performance:

  • Petrol System Cleaner – This innovative fuel additive removes deposits which build up on the fuel injectors, improving the life of your engine and improving fuel economy. Add a shot of Petrol System Cleaner each time you top up the tank for best results, or buy our helpful 4 pack
  • Lead Replacement – If you have an older classic car which still needs leaded petrol, you can use our Lead Replacement additive along with standard unleaded petrol to keep your car running.
  • Petrol Advanced Fuel System Cleaner – With its concentrated formula, Advanced Fuel System Cleaner offers an intensive clean, removing deposits which have built up on the injectors over thousands of miles. Use this product first to guarantee a complete petrol fuel system clean.


If you own a diesel car and want to extend the life of its engine and improve performance, here are the Redex products you should use in your fuel tank:

  • Diesel System Cleaner – Like our Petrol System Cleaner, this fuel additive can be added straight to the fuel tank, where it passes through the system to remove deposits, particularly around the injectors. This helps the diesel flow smoothly to the engine and prevents any build-up, for better fuel economy and a well-cared-for engine. You can buy it in a handy 4 pack to make topping up easy.
  • DPF Cleaner – If your car has a DPF, you might find the warning light comes on telling you it’s getting blocked. Using our DPF Cleaner will clear it, helping you avoid an expensive repair.
  • Diesel Advanced Fuel System Cleaner – Motorists normally invest in a diesel car for its longevity and economy when covering a lot of miles on the motorway. This high mileage can often lead to a build-up of harmful deposits in the fuel lines and injectors, so add a shot of Advanced Fuel System Cleaner for an intensive diesel engine clean-up.

Here at Redex, our innovative fuel additives can help improve the life of your engine, and we have a range of products to suit petrol, diesel and hybrid cars. For more information, click here to visit our homepage.