February 14, 2016

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.


  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 !

  3. Hi, filling up at Asda the tanker driver was beside me and I asked about additives, He said Asda has the engine additives and produced his bill of sale from the refinery in Grangemouth showing that he had the additives. Always buy Asda petrol now. No problems. And no kickback from services.

    • Ha Ha they may use additives on that day and what type did they add??

      Since when did you see a supermarket give something for nothing wake up people, if you buy a value product thats what you get simples they clean there tanks regular for a reason.

  4. Asda driver showed you a bill of sale for the additives… Awesome! finally someone solved the mystery of shite supermarket fuel! —Also— 5 years of Petroleum Engineering down the tube :)

  5. Volvo driver says:

    My Volvo v50 first went into “limp mode” on a long journey after filling the tank from empty at Asda. I always use Asda diesel as its cheap and convenient. When the car lost power I was on a dangerous stretch of the A69. After “limping” to a parking area I switched off and let the systems all reset. On restart everything was fine, to begin with, then the problem reoccurred until eventually the car cut out every mile or so. The vehicle was taken to a Volvo dealer and the first question they asked was “do you use Asda diesel?”. I was horrified. It turns out that my fuel filter was completely clogged and needed replacing. The filter was only 3 months old as it had been changed on the last service.
    I will never use Asda diesel ever again, nor any of the supermarkets for that matter. For the extra few pence a litre that I now pay for BP I more than get my moneys worth in enhanced performance, peace of mind and the reliability and safety from a much happier engine.

    • Border Reiver says:

      Good lad – you’ve joined the clan! Checked your mpg now? My (now) C30 does almost 60 extra miles to a tank full, so the extra pennies give extra miles. But, as everyone knows, nobody drives a C30 at more than 50mph :-)

    • Howard Carr says:

      Sainsbury’s fuel is BP. I have used nothing else for the last eight years with three Volvos and have been very happy with performance, clean running and economy – both petrol and diesel.

  6. I had the same problem with sluggish performance for years I used supermarket fuels,change to any big brand and noticed a big difference in performance and mpg.it all outweighs the pennies in litre prices and will never go back ,I have converted my daughter to this with big results from a dodgy starter to a smooth running car.
    Convinced there is a difference so we will never go back to supermarkets.

  7. From what I have read, most people are on about diesel, not too many people seem to use petrol now. Diesels don’t like short journeys, even more so one’s with DPF. I have been advised by numerous people not to have a diesel for my 8 mile commute. I have been using Morrisons petrol for about a year now in a 1.8T petrol A4 and get roughly 27-30mpg, mostly “extra urban” driving. I might try 44 litres of branded fuel to see if I get any extra from it. Very interesting reading this.

    • I have a Renaultsport Megane (2L turbo) and someone suggested I try Shell V Power petrol as it often suits a turbo aspirated engine. The difference was better performance and significantly improved mpg. I now get an extra 50 miles on a tank full and the extra mpg means that even using v-power it more than pays for itself. It’s a no brainier. I can’t recommend it enough.

  8. My experience with my first Ford Modeo TDCi (2003) was that it got to a point where it needed the injectors recoding every 6 to 9 months. Fortunately I got a Fordiag device and was able to do it myself but it seemed to become necessary more frequently as the car got older. I had been using supermarket diesel but then switched to BP Ultimate to give it a go. Almost immediately the engine was a lot quieter but within 2 weeks I had to recode after the fuel switch. However I had the car for over two years after that and constantly on the BP Ultimate during which time it then never needed recoding again. Would appear pretty conclusive there is a difference in quality. I also noticed a significant improvement in fuel economy, so much so that the supermarket diesel would need to be 25p a litre cheaper to be the same mile for mile fuel cost forgetting the injector recoding requirements.
    I now have a 2010 Mondeo TDCi and find it runs really well on BP Ultimate or Texaco Supreme but not quite as well on Shell V-Power. I gave this one a run on supermarket diesel and it was a lot noisier almost immediately and the fuel economy suffered. I won’t be buying supermarket diesel ever again.

  9. George allnutt says:

    I live in Cornwall and use texaco diesel fuel have found problems with it. The engine knocks
    On take up. My other cars have cat problems. When I fill up in south east engine is fine
    So must be the adertives they use in cornwall

  10. Rui Viegas says:

    I have a 2009 Diesel Corsa with DPF. In my area, premium diesel is about 10p/litre more expensive than regular supermarket diesel. I bought Millers additive, and, about 150 miles later, the car was running much smoother. I did the calculations and adding Millers makes the regular diesel approximately 3p/litre more expensive. Thus, one spends 7p/litre less by using the additive instead of premium diesel, while producing the same cleaning and performance effect.

  11. I bought a brand new Volvo V40 Cross Country and immediately filled it with diesel from my local Tesco; a fuel I never had an issue with in my Nissan Note. After as little as two weeks of ownership my engine check light came on so I pulled over and called Volvo Assist. The technician plugged my car into his laptop and frowned, he asked what fuel I was using and I told him. He advised using the top 3 (Shell, BP or Esso) wherever possible. It really is worth the extra few pence plus my local BP run a Fuel Save event when is you

  12. Driven Insane says:

    There are plenty of pieces around the net and in newspapers suggesting that ‘…..all diesel is mostly alike’ etc etc. Even the writer here has sort of alluded to all things being equal aside from the additives. But seriously, it just CAN NOT be right, can it?!!
    I know nothing about the petroleum industry, save for The Fractional Distillation of Crude Oil table that we all covered in chemistry. Yet I’ve heard enough anecdotal evidence from many motorists, and even more evidence from mechanics to figure out that supermarket diesel, especially ASDA’s, is not the same as that sold by the big oil companies. There’s enough just on this page, and it’s always the same story. Rough running, leading to blocked filters, and then complete failure. I was once told an apocryphal tale, the essence of which being that ASDA purchase their diesel from the bottom of the barrel, (literally), and that is how they always keep their prices low, not because it is a so called ‘loss leader’. I’m sure there’d be a lot of people employed within the industry who’d read that and yell “rubbish!”, “….that’s not how it works!” etc. But it sure would explain a lot.
    Either way, I’ve run a fleet of diesels for over 30 years, (long before they became the norm), starting with Renault 18 GTDs and Sierra 2.3DLs, and I NEVER have, nor would I ever use supermarket diesel, not even if they were giving it away.

  13. You never used supermarket diesel than what is your point to prove?

  14. I have a 2009 Corsa 1.3 diesel and my mechanic showed me what he had got out of an X Trail that was a bit sluggish like mine. It was like an emulsified sludge and when he asked the owner if he used Supermarket fuel he told him always from Morrisons. I immediately changed supplier to BP and felt the car was a lot better. Unfortunately I got an Astra petrol and passed the car to my wife who likes Tesco and uses it regularly. The car has spent 11 days at said mechanics as it developed a starting problem where it felt like it was missing on one cylinder then would pick up as normal and drive like normal. I booked it in to the garage for the mechanic to have a look but when he managed to get it started there was so much white smoke in the garage he had to push the car outside. He couldn’t start it after that. He has now drained the fuel and refilled with £10 of BP diesel and the car is going like a dream. Unfortunately the only evidence of my wife filling up is her credit card statement as the pay at the pump slips were out of action (as is quite the norm now!) so where do I stand about going back to them about the fuel being dodgy. Should I pay to have a sample tested? Before anyone says it sounds like she put petrol in, the car was run from nearly empty to just over half full before the problems started and a burn test of the fuel shows that it is diesel.

  15. Andy Reid. says:

    Many years ago, when unleaded petrol became manditory, a UK motorcycle magazine pointed out that in order to keep the RON Octane rating up, the calorific energy content per litre was dropped by as much as 20% by reducing the Toluene content substantially.

    This produced a noticeable drop in performance in all motorcycle produced up to the date of compulsory unleaded use in the UK.

    Two years ago I found a garage selling leaded 4 star petrol for classic vehilces and treated my 2 stroke 350cc bike to a 5 litres of the stuff….. it went like a rocket ship when compared to the normal ethanol super unleaded I normally used (and obviously didn’t have those damaging effects that ethanol has on fuel hoses, carbs, etc.). Once back on super unleaded the performnace dropped to the normal lack of enthusiasm in the top 20% of the rev range.

    My son rides a 1980’s commuter 125 to work everyday and we thought that the fact that the bike could only reach a grudging 55 MPH instead of the book top speed of 76 MPH was due to its age, despite having a rebore and engine rebuild. However a younger sibling version of identical specification but with only 4,000 miles on the clock was aquired and this also has the exact same problem, having the exact same lack of top speed and power compared to manufacturer’s original specifications.

    It is more than evident that the old leaded petrol gave far better performance than the modern ethanol stuff and didn’t destroy a vehcile’s fueling system or fuel tank during use.

    The problem for the fuel manufacturer’s was that they’ve had to start from scratch solving the Octane rating versus energy content of modern fuels.

  16. Dave Dunn says:

    We have two Skoda Fabia Diesel cars which we have had from new,
    Mine is a 1.9TDI my wife has a 1.4 TDI. We had always filled up at our local Asda store, I swore it ran better than the fuel from Tesco and Morrisons.
    Money was tight and fuel was fuel or so I thought.
    Last year my wife’s car developed a fault, every time it started up from cold it would emit large clouds of white smoke.
    Took it to a local garage who had a look at it, advised me it was a specialist fault and I needed to take it to a diesel specialist. They changed the wiring harness to the injectors (at a cost of £80)
    Still faulty and still blowing smoke and running shite. On a 3 cylinder car you notice a loss of power when only 2 work !!
    Injectors, £400 plus labour each !!!
    I was looking for another motor as I could not justify the cost of £1200+, or my suggestion, she waited till the engine warmed up and then it was ok.
    Just then, our local Costco store opened it’s new fuel station.
    After only 1 tank of fuel the problem stopped as quickly as it had started, it never as long as we could remember would climb a hill near our house in fourth gear.
    I fuelled up, it is like rocket fuel. More power, more miles per tank.
    And the best part, it is premium fuel with performance additives like you find at Shell and BP garages but, they sell it 2 to 3p cheaper than those dreadful supermarkets sell their ‘Base’ fuel as you call it.
    I’m told Costco currently have three stations, Sheffield opens one this month and over the next few years all of their stores will be selling high spec fuels below supermarket and most certainly below so called Premium brands. Premium Diesel today is 95.9p a Litre.

Speak Your Mind