The RIDE guide to...
It costs about the same as milk but petrol gives so much more enjoyment. So where does it come from?
Petrol. Where is comes from, how it’s made and what its qualities mean to you
OF ALL THE ingredients we need to enjoy our motorcycling, petrol is perhaps the most crucial. We spoke to industry expert Haltermann Carless to find out where it comes from.
Gasoline is derived from crude oil by fractional distillation, a process where the crude oil is heated at the base of the distillation column and depending on the temperature achieved and its weight, the by-product is drawn off for further processing. Gasoline is produced from 20-200°C, along with naphtha, both of which are the lightest by-products.
They then go through further processes to separate the two, before the resulting base gasoline is mixed with various additives to give it the required properties. Two key qualities tailored at this stage are the fuel’s calorific value and its density. The calorific value is the amount of heat (or energy) it produces at a constant pressure per kilogram and is expressed as Megajoules per kilogram or Mj/kg. The higher the value, the greater amount of energy released in combustion and the higher the resulting vehicle’s fuel economy is. The other quantity is the fuel density, expressed as kg per metre cubed, or kg/m3. Two different fuels can have the
same calorific value but
different densities; the higher-density fuel will produce more energy for the same volume of fuel burned.
Regular vs Super
Another quality of fuel is the RON, or Research Octane Number. The RON is an indication of the fuel’s resistance to detonation — the uncontrolled combustion of the air/fuel mixture within the engine’s combustion chamber. This can occur when the air/fuel mixture is ignited either before the correct point in the cycle by hot-spots or from more than one point, resulting in an uncontrolled burn and can have catastrophic effects on engine performance and components.
Better detonation resistance means the engine can run a higher compression ratio and/or increased ignition advance to improve efficiency and output. That’s why some high-performance car manufacturers, for example, specify 98 RON fuel for their lairiest models.
Which brings us on to ‘Super Unleaded’ fuels. Regular pump fuel will typically have a RON of 95 but many ‘Super’ fuels will be 98 RON. They may also have additional additives, such as detergents, for example but according to
Haltermann Carless, you are unlikely to notice any additional performance purely from this increase in RON, unless you have made performance-enhancing modifications to the engine.
Ethanol
As part of an ongoing drive to reduce reliance on fossil fuels and the harmful emissions that contribute to climate change, manufacturers have been introducing ethanol into fuel for some time. Ethanol is an alcohol derived from fermenting sugars and therefore, is considered a renewable fuel, producing less ‘greenhouse’ gases than a comparable volume of pure gasoline. It also has better anti-knock properties than petrol, so it can help achieve excellent RON numbers. However, it has a lower calorific value than gasoline, so fuel economy is lower.
It can also have a negative effect on some of a bike’s components; it may accelerate the deterioration of fuel lines and seals within the fuel system or cause some plastic fuel tanks to balloon. Haltermann Carless recommends checking with the manufacturer of older bikes if you’re planning to use fuel with an ethanol content of 10% or more.
Is it worth adding additives?
Should you use standalone additives in your fuel? Haltermann Carless reckons they can be useful if you’re looking for specific benefits. However, it also warns many overstate their effectiveness and you should rely on your own judgement as to whether they are worth it.
While on cost-effectiveness, there is a constant debate whether supermarket fuel — typically cheaper than forecourt fuel — is any good. According to Haltermann Carless, all fuel sold in the country must meet a minimum standard — EN228 — and that, for logistical reasons, the majority of ‘base’ petrol in a particular region will have come from the same refinery with the individual brands adding their own additives. Turnover is usually pretty quick too, so there shouldn’t be any ageing issues.