Premium diesel and petrol – do they work?

Car ownership advice
Premium unleaded petrol (gasoline) and premium diesel – are they worth it?

“Does premium diesel work or is it just a waste of money?”  Asked by a Google searcher, August 2012.

Most fuel brands offer ‘premium’ options for both petrol and diesel fuels, which are usually priced about 10% higher than their ‘regular’ fuels. They usually claim to give you more performance while using less fuel. So how much gain do you get, and is it worth the price premium over regular petrol or diesel fuels?

What is premium unleaded petrol?

Premium unleaded petrol is usually a more refined form of petroleum than regular unleaded, with a higher octane number. This makes it burn more efficiently, thus delivering more power for less fuel burned. It may also have additives such as detergents to keep the inside of the engine clean.

The level of improvement you can expect to get from premium unleaded petrol will depend on your engine’s requirements, and your driving style and circumstances.

Some engines, usually in higher-performance cars, require premium unleaded at all times and will suffer reduced performance and fuel economy if you use regular unleaded.

Other engines will see very little difference at all; if your driving is predominantly city commuting and school runs, you probably won’t notice any significant improvements. If you tend to drive harder or do more open road driving, you may notice more substantial differences.

What is premium diesel?

Similarly, premium diesel fuel is usually a higher quality of fuel which burns more efficiently. It may also have additives which help keep the engine clean and improve cold-temperature performance.

There is usually less difference in performance and economy between premium diesel and regular diesel than you get with premium unleaded petrol and regular unleaded for a single tankful.

However, premium diesel will potentially help your engine run smoother and cleaner, which can improve both performance and economy with regular use. This may be more noticeable on older or higher-mileage engines than in a brand new car which hasn’t yet accumulated any sediments within the engine.

Try it and see

The best way to discover if premium diesel or premium unleaded petrol work for you and your car is to try about three tanks’ worth and see if you notice a significant and repeated difference.

If you can’t feel any improvement in performance and you don’t appear to be getting greater mileage from each tank, you’re probably better off sticking with regular petrol or diesel. If you do notice improvements, you need to decide whether the increased cost (which can be up to 10p/litre) is justified.

Recommended reading:

Are diesel cars suitable for city driving?: How suitable are diesel cars for urban driving and short journeys?

Fuel economy: petrol or diesel?: Should you buy a petrol or a diesel car?

Fuel economy: real-world vs. official figures: Why is there always a large difference between the claimed economy figures and what you actually get?

fuel economy - premium petrol or premium diesel - the car expert

Stuart Masson
Stuart is the Editor of The Car Expert, which he founded in 2011, and our new sister site The Van Expert. Originally from Australia, Stuart has had a passion for cars and the car industry for over thirty years. He spent a decade in automotive retail, and now works tirelessly to help car buyers by providing independent and impartial advice.


  1. Hi Stuart,
    What happens if both premium and plain unleaded petrol is put into the tank? Say half premium and half plain? Will the engine explode? I am asking because I have a loose memory and will surely forget what I have put into the tank last time!


  2. I think it’s all a con, and that it’s probably exactly the same fuel in the regular and premium pumps. Just an excuse for blood-sucking oil companies to screw us all over yet again.

  3. Stuart Masson

    Hi Adnan. For your car, it will make no difference at all. Your Toyota will run happily on regular unleaded petrol, although you may get slightly more power and/or better economy on premium unleaded. So you definitely don’t need to worry about it. If a certain engine is designed to run on premium unleaded, it will not run cleanly on regular unleaded and over time may misfire and develop problems. However, it is not going to cause the engine to explode or anything dramatic like that.

    Best wishes, stuart.

  4. V-Power Diesel is a blend of regular petroleum-based diesel and synthetic diesel , created using gas to liquids (GTL), along with some extra additives designed to clean the injection system and improve injection pump and injector lubricity.

  5. Hi! I have been trying this for the last fortnight, and seem to be getting better mileage from premium petrol. I worked out that it’s costing me about the same, but I guess it’s probably worth it in terms of being better for my engine, isn’t it?

  6. I have been trying this experiment in my diesel Astra for the last couple of months, and I can’t really tell the difference. So I’m going to stick to normal diesel.

  7. stuart

    It can be very bad for it. Not a good idea.


  9. what happens if water is mixed with petrol and is let the engine run?

  10. i have a 2012 mini countryman would it make any diference to the performance?

  11. stuart

    Hi Anne. You probably won’t notice much difference in performance, unless you really drive your car hard, but you might find the economy is better. With the fall in petrol prices lately, it’s probably a good time to give it a go, since premium is cheaper now than regular was a few months ago.

  12. I’ve just had Diesel Bug identified in my Jaguar XF. So no more cheap supermarket diesel for me.

  13. Hello ive recently purchased a Yamaha MT-125 ABS it it recommends using prem unleaded with a octane number of 95 or higher im just wondering if it will cause problems mixing reg and prem unleaded fuels. this is probable a silly question but the bike is the first vehicle ive ever brought or owned.

  14. Stuart Masson

    Hi Tony. If you are in the UK, regular unleaded is 95 octane anyway, so you shouldn’t have any problems. Whether or not you get better performance and/or economy running premium unleaded (97-98 octane) will depend on your bike’s engine, but it certainly shouldn’t cause any problems running a mix of the two.

  15. where can i get premium diesel in NW London will I get better performance from my 2016 Kia Ceed Crdi 7 speed dct

  16. Stuart Masson

    Most service stations will offer both regular and premium diesel options. As for whether it will give better performance, it’s unlikely to be noticeable. Your car is new, so it’s unlikely to have accumulated any significant sediments in the fuel system which would be affecting the engine performance.

  17. I have the Maserati Ghibli Diesel, should I only use Premium Diesel as this is a high-performance car and will this help the engine to warm up quicker and thereby let my DPF work better?

  18. Stuart Masson

    Hi Jisan. If your car is new, it should not give you any great benefits in terms of improving performance or economy. Premium diesel is designed for cleaning out diesel fuel systems, but it is unlikely your car’s fuel system will be clogged up unless you have put a high number of miles on your Ghibli.

  19. Thanks for the reply Stuart, much appreciated.

    I am from Denmark and my Ghibli was bought in Denmark when it had gone 7.500 miles, so I guess its still considered as new.
    I have driven another 5000 miles so all in all it has gone around 12.500 miles.
    My only concern is the DPF if it works as it should. I use my Ghibli Diesel as my weekend fun car which I drive approximately 20-25 minutes trips or longer to dinner/events/shopping with my wife and then I have a Citroen C3 for every-day driving.

    But to understand it correctly the Premium diesel does not help the Diesel Particle filter in any way ?
    And since my Ghibli is my weekend-car I should do longer drives of minimum 25 minutes on each drive to keep the DPF working properly even if this car is from end-2014?



  20. Dear Jisan,

    I have a 210.000 km Euro 4 Alfa 159.

    Feel free to use all sort of diesel, as the newest is injection system, more precise and clean is the burning cycle. What you have to be absolutely perfect is oil and filters check and replacing. A friend of mine is a motorist, involved in motorsports, and he has a 500.000 opel astra that is taking to 1M km. He suggested to avoid special fuels as they clean very well, and for this reason the risk is to clean lubrication too. His opinion is to invest in oil and fuel frequent changes, every 20.000 kms at least. Feel free to ask me more information. Enjoy your Maserati, it’s a pleasure to know there are people passionate in so refined mechanicsm

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