November 30, 2015

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.Pistonheads

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.


  1. Hi all. Shell V Power/BP Ultimate vs Supermarket diesel. A case history, not scientific, but from some one who has driven nearly a million miles (now retired thankfully)
    Have a 1.6 Hdi Focus bought new, now with 18k miles, and much loved. Initially started with the S/mkt stuff as it was convenient and it seemed ok. My neighbours son accidentally put VPower diesel in their Merc with amazing results. In a way this was a blind test as ‘dad’ didn’t know about the super fuel in the tank. He just noticed the increase in performance and economy. So I said I would try the same for the sake of a few quid. Ran the tank to near empty and filled with Shell VPower diesel. The car felt different after about 50 miles and even better after 300. Economy improved markedly on a regular 220 mile round trip (mostly dual carriageway but 25% urban). At the time I calculated that it was costing me 8% more to fill up but with a 10% improvement in mpg. (Checked by filling brim to brim not the car’s read out) Apart from that the car ‘felt’ better.
    Ford Dealership confirmed that they have similar results and they’re not selling me fuel.

    When the prices dropped a few months ago I balked at the difference between Shell V and the very low Asda/Sains/Tesco prices. A massive percentage. So I reverted to the S/mkt stuff. The car just never felt lively and mpg was reduced (on the same regular run). After about 1000 miles of that I decided to bite the bullet.

    With about 5lts left in the tank, I filled up with BP Ultimate last week. The improvement was evident within 50 miles, performance and mpg as previously with Vpower and the car is noticeably quieter. I don’t know how this happens but it does. My regular 220 miler is tomorrow so will be checking carefully. May feed back on that.

    • Border Reiver says:

      I used to have a diesel Peugeot 407 SW. It used to block the particle filter regularly – the car would not accelerate, had to change down on minor rises (A.1 above Morpeth) etc. No ‘GO’!
      Car was looked after by a retired guy who had been Foreman in a main dealer workshop. He asked what I was filling it with. I told him it was Asda special. He advised running the fuel right down and brimming the tank with Shell VPower, which I did. The car ‘flew’ (almost) and added an extra 50 miles to a tank full.
      I no longer need a larger car so have bought a s/h Volvo C30 – 2L 6 speed Diesel. The vendor
      recommended VPower – I said, “You are talking to the converted”!
      I do 6 x 650 mile (in a day!) round trips a year, + normal daily running around. I do not hang about on the long runs! The on-board computer holds a steady 52.5 mpg all year round.
      OK, extra cash at the pump, but for driving pleasure and great mpg, I figure it’s worth it.
      Shell would not make the stuff if nobody bought it! Do yourself a favour and (with a clean dpf) and try it. You’ll be amazed.
      No, I do NOT have any connection with Shell Fuels.
      p.s. Next 650 miler is Xmas day – not much traffic about – I’ll let you know.

  2. Had an uncle with garage who every other year cleaned out diesel tank in ground as full of fatty sludge ! So even the storage tanks sludge up as well as vehicle tank , hence the need for additives , cousin advised on when their were no additives in the base fuel as it was quicker to fill tanker ! Both sadly passed away due to cancers , my own experience as a county manager in my beamer was that my fills @ Sainsbury every week was that the evening one coincided with delivery by bp tanker so assume it was .Had a knock so took to dealer after brand fill up who said supermarket fuel was problem really ? .Took car to local injection specialist who said system clean and knock from cooling system ! & turned out to be plastic component in system so dealer will blame most convenient non cost source . I converted to a diesel dpf and from the start used millers and never had a problem as bought by the box for the years I had it . Now have van & suv which is known to have dpf problems if short journey so bought some similar additive to ensure fuel is burnt off as the dealers burn your fuel off if you get dpf block anyway , so its preventative & cheaper as mpg better by a little . All supermarkets can buy on the spot markets where the source is dubious so base quality is variable hence car makers must choose a base for predicting mpg so will opt for brands .Also most fuel is produced for the average motorist who wants mpg and cheaper ! My ethos is cold weather is what sorts out the best from the worst and prefer to add my own mix as I know what I am getting and have noted the difference when I had the beamer as octane is everything in high performance so which ever way you choose you pay , the arch choice is yours !

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