Our guide to different types of fuel - Petrol vs Diesel

Our guide to different types of fuel - Petrol vs Diesel

Not so long ago choosing a fuel type was pretty simple. You either went for petrol or diesel, and that was job done.

Now there are a myriad of different fuels, each with many different classifications. Check out our guide to see what it all means.


This is the most common type of fuel in the UK. Bio Ethanol is mixed with Unleaded Petrol for the most environmentally friendly mix.

It can usually be bought as either Premium Unleaded (95 RON) or Super Unleaded (97/98 RON). You may also be able to purchase high-octane unleaded from some retailers, such as Shell’s V-Power Unleaded, which goes up to 99 RON.

What does RON mean?

RON refers to the octane rating. This measurement determines the ease at which the particular fuel will ignite inside the engine's cylinders. The higher the rating, the more difficult it is to ignite as it requires greater compression.

However, once it does ignite, it will burn at a higher temperature than lower-octane rated fuels. This means it can burn more efficiently and can increase performance.

Should I buy higher RON?

The simple fact is that most Unleaded Petrol vehicles should just stick with standard Premium 95 RON petrol. This is because most engines will get very little or no benefit from higher-octane fuels.

The only vehicles that can benefit are high-performance cars with larger engines - many of which use turbochargers or superchargers to increase the fuel compression inside the cylinders. Some of these vehicles may notice an increase in performance from the higher-octane fuels.

In addition to performance and economy benefits, higher-octane fuel manufacturers - such as Shell V-Power and BP Ultimate - claim their fuels will also aid with increased engine lubrication and cleaning. That’s despite BP Ultimate only having a RON rating of 97.

If your vehicle is remapped, it may be mapped to a particular octane level. Remapping - sometimes called Chipping - is when third party software is installed on the Not so long ago choosing a fuel type was pretty simple. You either went for petrol or diesel, and that was job done.

Now there are a myriad of different fuels, each with many different classifications. Check out our guide to see what it all means. that changes parameters such as how much fuel enters the engine, the compression level of the fuel and boost settings for the turbochargers. Modifying these parameters can affect things such as fuel efficiency and performance.

Having a high-performance map on your car’s ECU often means you’ll need to use higher-octane rated fuel to benefit the most from the map. Whilst lower-octane fuels won’t damage the engine, it may result in sluggish or jerky combustion compared to the unmapped car. Always ask your car tuner which RON they recommend for the map you have installed. Also note, remapping nearly always invalidates your vehicle warranty. 

Types of Petrol

New EU rules introduced to standardise fuel labelling has meant that there are now new labels for all the different types of fuel based on their biofuel blend.

Petrol, for example, which is blended with Ethanol, has the label E, and comes usually in either E5 or E10 format. There is only really one that is sold mainstream in the UK: E5. The 5 is because it has 5% Ethanol, and 95% Regular Unleaded. E10 naturally has a 10%/90% ratio. Since it has more ethanol and less petrol it is greener and better for the environment.

Since 2011 all new petrol cars have been E10 compatible but the Society of Motor Manufacturers estimate that only 8% of petrol cars are actually E10 compatible. For now E5 remains the fuel available at most petrol stations across the UK. 


Like Petrol, there is more than one version of Diesel. They have what’s known as a Cetane CN rating - between 45 and 55. Like octane, the higher the cetane rating, the more efficiently it will burn, giving similar economy, performance and cleaning benefits as higher-octane petrol fuels.

Standard diesel is now referred to as B7 - due to its 7% biodiesel content. There is a B10 - available in France - but not all cars are compatible with it, so always check the fuel type your car accepts when travelling abroad.

Diesel used to be the fuel of choice for commuters and businesses who drive a lot of miles. That’s because diesel is more fuel-efficient than petrol. This is the reason most of the taxis you see (apart from the more modern electric ones) are diesel, rather than petrol.

As part of a push to reduce Carbon Dioxide (CO2) in the atmosphere, the UK reduced tax on diesel due to the fact it produced 15% less CO2 than petrol. As you could expect, the sales of diesel vehicles rocketed. Between 1995 and 2016 the market share for diesel vehicles went from 10% to 50%!

Unfortunately, it has now been discovered that diesel cars produce four times the amount of Nitrogen Dioxide (NO2) and 22 times more particulate matter - known for penetrating the brain, heart and lungs. Essentially, diesel is much worse for both the environment and people’s health. As a result, diesel is now taxed more than petrol.

Modern diesel cars are fitted with a particular filter to mitigate this problem, but if you do a lot of town or city driving this can become clogged. So a diesel vehicle is better-suited to longer distance driving.

Volkswagon Emissions Scandal

In additional to this, the now infamous Volkswagon Emissions Scandal caused another huge blow for diesel. Many Volkswagon diesel vehicles were fitted with special software to detect emissions tests, which meant that the readings were falsified and gave the impression they were less environmentally damaging than what they actually were. When this came to light a lot of people were stuck with diesel vehicles (that they were pushed into buying through various government campaigns) that were now frowned upon.

As a result of all this, diesel sales are now dramatically falling, and petrol is back on the uptake. That said, it is Electric Vehicles now that are really gaining traction.

Ultra-Low Emissions Zone 

There is now an Ultra-Low Emissions Zone in London - with many more cities looking to follow suit. It follows the same boundaries as the Congestion Charge zone (currently £11.50 per day between 7am and 6pm) but adds an additional £12.50 to the cost and applies 24 hours a day, 7 days a week. All diesel vehicles that do not meet Euro 6 standard have to pay, with petrol cars needing to meet Euro 4 standard. Electric vehicles are naturally exempt, due to their zero-emissions.

Electric Vehicles (EV)

It’s been coming for many years but electric vehicles are now taking the UK by storm. With Tesla’s being the first to be mass-produced and sold, nearly all manufacturers are now producing either hybrid or fully electric vehicles.

Fully electric vehicles produce no emissions at all and so are exempt from vehicle excise duty. They often come with a higher initial price tag than petrol or diesel cars, but running costs are around 75% less, so if you drive a lot of miles then an EV could be a financially wise (and environmentally friendly) option. You may also have the option of recharging your car at home and be able to skip the dreaded “fuel stop” on the way home from work. For more information check out Is it time to buy an electric vehicle?.


Unless you’re driving a considerable number of miles, we’d always recommend petrol over diesel. It’s cleaner and cheaper. If you’re thinking more long term and are happy to pay the initial higher price tag, an Electric Vehicle may be for you.

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By Niall St John

Niall is the Co-founder of DriverBuddy and loves his cars!