A new section – this month tackling pricey ‘advanced’ fuel available at the garages.
DO ENHANCED HIGH GRADE AND HIGH OCTANE FUELS GIVE YOUR BIKE MORE POWER?
If you believe the hype, the enhanced high octane fuels available from the forecourt can transform your ride into a fire-breathing, petrol-sipping, eco-friendly monster. But is that really the case?
L eaving your bike’s flower tickling emissions and fuel economy to one side for a minute (okay, indefinitely), do high spec fuels like Shell V-Power Nitro+ actually endow your motor with more power? Or is the price premium over normal petrol just money up in smoke? It’s relatively simple to dyno test fuels back to back – so we took four of the UK’s favourites and gave them a chance to show us their worth…
Fire up the dyno
Armed with an 8,000-mile-old, Yoshi exhaust-kitted GSX-R600 L3, the first fuel we put to test was Tesco Momentum99. As with all the fuels we tested, we took the highest number from multiple dyno runs. The Suzuki topped out on Tesco’s top fuel with 116.16bhp. Not a bad effort, but could it be bettered?
After sucking the GSX-R’s tank dry, Shell’s standard unleaded got its chance to shine. After drinking down a good few litres, the bike burped out 115.93bhp. Next came a fresh tank of Tesco unleaded. Would the cheapest fuel here hold the screaming 600 back? Not really, it turned out. At 115.99bhp, it’s not even half a horsepower off the most expensive fuel on test, which is good to note if you like to look after your pennies.
Finally, the most expensive fuel on test got its turn to showcase its benefits, Shell V-Power Nitro+. We purged off any remains of the last fuel from the tank before the Gixer was treated to some of the good stuff. It’s got a fancy name and costs 15p a litre more than the cheapest fuel tested, which didn’t really go to count for much, as it made just 116.28bhp.
Money to burn
Okay, all the fuels here made within 0.35bhp of each other, that’s not even 1% of a difference. In fact, that’s way larger than the difference between the GSXR’s best and worst runs on the same fuel. The most striking thing about the whole test is how close the four fuels’ best runs were to each other. So, based purely on peak power output, expensive, high octane fuels are unlikely to give you any significant benefits on a relatively stock bike. However, tuned bikes running raised compression ratios and advanced ignition could most certainly extract a little extra oomph from high octane petrol. But that’s a test for another day.
Modern petrol is a blend of many hydrocarbon fuels but, historically, petrol was mainly a combination of iso-octane and n-heptane. Iso-octane is very good at resisting knock and n-heptane isn’t. The ability any given petrol blend has at resisting knock is measured, using a special test engine, and given a Research Octane Number (RON) rating. 100RON fuel is equivalent to 100% octane content and 0RON equivalent to 0% octane (100% heptane). 100RON isn’t the limit for petrol though. Other hydrocarbons, and alcohols are even more knock resistant than octane. Race fuels can have RON numbers well over 100. But high octane fuels don’t necessarily make more power, they just allow an engine to run higher compression ratios and more ignition advance.
Knock, compression ratios, ignition timing and power – knock is when the fuel inside the combustion chamber destructively explodes rather than burns. The supersonic pressure wave from the explosion creates that rattly, tinkle noise. Don’t be deceived though. That innocuous noise tells you serious engine damage is imminent.
High compression ratios and advanced ignition timing lead to high combustion pressures and temperatures. These higher combustion pressures can push harder on pistons, thus making more power. The limit on how far you can go with compression and timing comes from the fuel being used and eventually it will spontaneously explode rather than burn.
As most modern bikes still use mapped, rather than dynamic ignition timing, the factory needs to set the ignition point to conservative, safe levels that won’t ever knock in normal use with standard pump petrol.
More than just octane
What we didn’t test were the additives that Shell and Tesco have put into their fuels. All pump petrol benefits from additives when leaving the refinery. Detergent additives help to keep your bike’s fuel system free from deposits and contamination. Corrosion inhibitors prevent moisture in the fuel from attacking injectors, tanks, fuel lines etc. Anti-aging agents, called oxidation stabilisers are added to prevent the fuel from oxidising, i.e. stopping the petrol from ‘going stale’. But the high spec fuels are treated with an enhanced additive package that also boosts octane ratings. It is reasonable to assume that high spec fuels with enhanced additives afford some cleaning benefits for your engine or may not go stale as quickly. But whether you’re prepared to pay a premium for them is entirely up to you. As far as outright performance is concerned, there’s not a lot in it. As for me, I’m happy sticking with the cheap(er) stuff.
With thanks to:
Willie at Dynotech Ecosse. Call today to get your bike fuelled to perfection: 0141 882 0632