“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.
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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?