Choice at the pumps might be limited to a couple of petrol variants and one or two diesels, but venture away from your local filling station and you’ll find a much wider variety of fuel, including happy juice to suit your Vauxhall in fast-road and race environments.
In the wake of the recent Volkswagen emissions scandal (a chain of events triggered when the United States Environmental Protection Agency issued a Clean Air Act notice of violation to the German car maker after discovering it intentionally programmed more than eleven million turbocharged direct injection diesel engines to activate emissions controls only during laboratory testing), diesel has had a bad name. In response to the crisis, VW’s sister company, Porsche, has axed all current diesel variants from its line-up. Even so, there are plenty of diesels left on the road, and we’re no longer driving in the age of smoky 1.5-litre Novas pushing 50bhp!
Despite VW’s woes, diesel technology has been much improved in recent years. Most manufacturers have an impressive array of turbocharged diesel engines in their product portfolios, and most prove to be viable platforms for tuning projects. As already mentioned, due to the fact that a diesel engine makes use of compression ignition, diesel fuel possesses a low octane rating, meaning it self-ignites with ease. Thankfully, due to the nature of diesel, detonation or pre-ignition isn’t a concern (unless operating temperatures are uncharacteristically high), which means a low octane fuel doesn’t present the same challenges as it would if being fed into a petrol engine.
Although not massively popular, performance diesel fuels have an increased cetane level, which is a general measure of diesel quality and an indicator of how rapidly the fuel combusts. In theory, diesel fuel with a higher cetane level should offer improved performance at higher rpm.
By far the most common fuel. In the UK, forecourt petrol tends to be 95RON for regular unleaded, or 97-99RON for the various brands of super unleaded. It’s recommended most performance and all tuned cars are powered by super unleaded. While it doesn’t compare to a true race fuel, impressive results can still be achieved. We’ve featured countless tuned cars with over 250bhp per litre using 99RON fuel bought from regular filling stations. If, however, you want to reliably make use of high compression and high boost pressures, then you’ll need to consider the benefits of a different blend of fuel, such as many of those listed below.
The term ‘race fuel’ is very broad, but for the purposes of this article, we’re referring to high octane petrol-based fuels specially blended with various chemicals for maximum performance. There is a wide variety of race fuels available. For example, C23 boasts one of the highest octane ratings, coming in at more than 130RON. It’s hugely resistant to detonation. Many race fuels are oxygenated, which means (go on, have a guess!) the fuel has oxygen molecules suspended within it. In essence, this means more power can be achieved when compared to non-oxygenated fuel with a similar octane rating. Ideal for tuners of naturally aspirated engines looking to unleash every last pony!
Liquified Petroleum Gas (LPG) is almost always used to save money. It’s difficult to ignore pump prices, where LPG is approximately half the cost of petrol. What you may not realise, however, is that LPG has a very high octane rating and is supercold. In other words, it’s resistant to detonation, giving it heaps of performance potential. That said, you can’t simply load your car’s fuel cell with LPG in the same way you would fill up with race fuel. Instead, you need a completely different injection system fitted alongside stock fuel equipment, enabling the driver to switch between LPG and factory-specified fuel at the quick-and-easy touch of a button.
Usually reserved for drag and hardcore circuit weaponry (including Indy Car contenders), methanol is rarely used as a main fuel, but is often injected as an anti-detonation aid for forced induction applications,