Should I Use Premium Fuel?
Every driver has seen the premium fuel pump, but do any of us really know what it is? How does premium fuel differ from regular fuel? Will it increase my mpg? Or increase hp of my vehicle?
Premium fuels will often cost up to 10p more per litre to fill up with compared to standard fuels. So what benefits, if any, can you expect to gain from this extra outlay?
Premium Petrol vs Standard Petrol
Petrol engines use cylinders, pistons, and spark to power the movement of mechanical engine parts. Within the cylinder lies a mix of petrol and air, this is compressed by the upwards movement of a piston which makes the mixture much more flammable. A spark plug then fires and the mixture is ignited, a hot gas is created which pushes the piston back down again and as the piston is attached to the crankshaft, the crankshaft is turned creating mechanical power to drive the car.
Premium petrol is likely to have a higher octane rating of around 98, compared to the standard 95. The octane rating relates to the compression that occurs in a petrol engine cylinder. It tells you how much the fuel can be compressed before it ignites spontaneously instead of due to spark from the engines spark plug. The higher octane premium petrol can be compressed more than the standard form.
Fuel igniting on its own before the spark can reduce the performance and efficiency of an engine. The engine will not be functioning in the most desirable way, fuel is being wasted by random combustions that do not help power the vehicle. Spontaneous engine combustions also cause what is known as ‘knocking’ in the engine. Knocking can cause damage to parts of the piston and cylinder, which will eventually need to be replaced, so reduce the durability of the engine.
So, premium petrol may have the power to increase hp, increase mpg and reduce damage to the engine … but not for all cars.
The cars that are likely to feel the most benefit from premium petrol are high performance cars. This is because superchargers or turbochargers are used to create higher compression ratios in the cylinders, to produce more mechanical power. To do this higher pressures and higher temperatures are created which makes fuel more likely to ignite spontaneously and ‘knocking’ a greater risk. If a higher octane petrol is used, such as the premium version, the fuel can withstand a larger amount of compression so reducing these risks.
Drivers of cars whose engine is built for performance may notice improved throttle response, improved efficiency, and increased power by using a premium petrol. However, any benefit will also be affected by the types of journeys you are making and your style of driving. If you are driving a car with a smaller, non-performance, engine on short trips around town it is unlikely you will notice any benefits from using premium fuel. The only time a benefit may be felt in this situation, would be if the premium petrol used had extra additives. Some premium petrol includes chemicals within it which help reduce friction and clean the engine helping everything to work more efficiently.
A diesel engine works slightly differently to a petrol engine – there is no spark involved. Air is placed under great pressure in combustion chambers, creating heat. When the air is hot enough, diesel is injected into the chamber where it ignites spontaneously.
This difference in the way a diesel engine works, makes a great difference to the use of premium diesel. For this reason, premium diesel is unlikely to feature a higher octane rating. The diesel fuel is usually made premium by the addition of additives which will help clear out sooty deposits in the engine and ensure the engine is working as efficiently as possible. Depending on the vehicle, style of driving and journey taken this could result in more mpg and better performance. So for any diesel vehicle, high performance or not, there may be a benefit to splashing out on the occasional tank of premium fuel.
Are there any cars which require premium fuel?
To find out which type of fuel your car needs you can check inside the filler cap. This information is often given there. If not, you will need to plough through the owners manual until you find which fuel the manufacturer recommends.
Some cars, usually high performance petrol vehicles, will have engines designed to run on premium fuel. If you ignore this recommendation and use standard fuel you are likely to notice lower performance and risk engine damage from ‘knocking’.
Have You Ever Used Premium Fuel?
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