Is All Petrol & Diesel The Same?

Filling up car with fuelIt’s a common question that often triggers big arguments.

Is branded petrol and diesel better than supermarket fuel, or should you just buy the cheapest you can find?

The problem is that most people don’t know how the fuel business works, and the truth is a well-kept trade secret. Let me explain.

The Easy Bit – Premium Fuels (Shell V-Power, BP Ultimate, etc.)

We’ll start with the easy bit.

Premium fuels, such as Shell V-Power Nitro+ and BP Ultimate, are not the same as regular petrol or diesel , although you can mix them freely with standard fuels without problems.

Petrol like this is known as ‘super unleaded’. Confusingly, the petrol that is labelled as ‘premium unleaded’ on forecourt pumps (e.g. Shell Fuelsave) is actually standard petrol. When it comes to fuel, super is better than premium!

These ‘super unleaded’ fuels cost several pence per litre more than regular unleaded. For this extra money, you get a different, more sophisticated package of additives for cleaning and lubrication, and fuel with a higher octane rating.

It’s a similar story with ‘super’ diesels, like BP Ultimate Diesel.

Octane (petrol) and cetane (diesel) ratings describe the way a fuel burns inside an engine. Broadly speaking, a higher rating means a fuel will burn more efficiently and effectively inside your engine. This may improve performance and/or economy slightly – although not all drivers will see a noticeable difference.

Some supermarkets also offer their own super unleaded — notably Tesco, which offers Tesco Momentum 99 octane. This is usually cheaper than Shell V-Power or BP Ultimate, but opinions vary as to whether it provides the same engine cleaning and mpg improvements as the top two fuels.

Another point is that Tesco Momentum 99 super unleaded reportedly contains more ethanol than super unleaded fuels like BP Ultimate. This provides an octane boost but some people believe it doesn’t provide the same efficiency gains as the more expensive branded fuels.

Like everything to do with fuel, people have different opinions, and the facts are hard to find.

Standard Unleaded and Diesel Fuels

The big debate is over whether the standard petrol and diesel sold by supermarkets is the same quality as that sold by branded fuel companies like Shell, BP, Esso and Total.

Let’s start with some known facts:

All fuels sold in the UK conform to the relevant British Standards. This means that they should all work in roughly the same way and you can mix them freely in your car’s fuel tank.

The standard petrol and diesel that’s sold on garage forecourts is mixture of two things:

  • ‘Base’ fuel
  • An additive package

The base fuel is the same for all companies – in fact, it usually comes from the same tanks at the local fuel refinery/distribution centre. What varies is the additives package that goes into the fuel. These additives packages are secret recipes of extra ingredients that help keep the engine clean and improve lubrication inside the engine cylinders.

Each fuel company has its own additives packages and these are different. So it is possible (but not common) for some drivers to feel that their car responds better to the additives used by one fuel manufacturer over those of another.

What About Supermarket Fuels?

There are all sorts of stories that go round about supermarket fuels, but the fact is that supermarket fuel tanker lorries are often seen filling up from the same tanks as branded fuel lorries (e.g. Shell, BP) – so the chances are that most of the time, the fuel they sell is the same, although again, it may have different additives packages.

However, one common story about supermarket fuel is that some supermarkets don’t have a regular fuel supplier. Instead, they buy odd lots of fuel from wherever it’s cheapest, including abroad. This could (if it happened) lead to supermarket fuel having a more variable set of additives than branded fuels.

Not many people really know the truth about this business, and they are not the kind of people who will reveal all on the internet. Unfortunately, that means we will have to keep guessing as to whether there is any meaningful difference between supermarket fuels and branded fuels.

As you can see from the many comments below, many drivers have strong (and opposing) views on this subject! Feel free to join in the conversation.

152 thoughts on “Is All Petrol & Diesel The Same?

  • April 11, 2018 at 5:45 am
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    There’s a lot more to engine reliability and performance than fuels and additives. You can put Shell this and BP that into your car but if you’ve not serviced it for years then the performance will suffer. My new focus Derv runs great on Tesco fuel, I asked Ford if a particular brand of fuel was preferred and the sales manager said ‘We can’t tell what brand you use so it has no effect on your warranty’. In 2 years when the warranty expires, the car goes back and I get a new one. My old M3 got the very best Petrol and the very best service. It was fantastic and completely dependable.

    So all I’m saying is, If your putting expensive fuel in your car expecting a better return. Have it serviced regularly and with quality oils and parts and it most likely will.

    Reply

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