October 23, 2014

Is All Petrol & Diesel The Same?

Is all petrol and diesel the same, wherever you buy it from?

It’s a common question that often gives rise to heated debate between people who swear that their car runs better on fuel from XYZ Company and those who say that it’s all the same and they just buy the cheapest.

The problem is that most people don’t know how the fuel business works, and the truth is a little harder to find.

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

Let’s 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 fuels, although you can mix them freely with standard fuels without problems. Petrol like this is known as ‘super unleaded’ — confusingly, what is labelled as ‘premium unleaded’ on forecourt pumps (e.g. Shell Fuelsave) is actually standard petrol.

These ‘super unleaded’ premium fuels cost several pence per litre more, have a different, more sophisticated package of additives for cleaning and lubrication, and have a higher octane rating (petrol) or cetane rating (diesel).

Octane and cetane 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 cleaning benefits and mpg improvements that are claimed for the top two fuels. Tesco Momentum 99 super unleaded reportedly contains more ethanol than super unleaded fuels like BP Ultimate, which some people claim provides an octane boost but may not 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 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. 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, so we will have to keep guessing as to whether there is any meaningful difference between supermarket fuels and branded fuels.