WHAT’S IN AN ADDITIVE?
Fuel additives come in many distinct flavours:
1 OCTANE BOOSTERS
These are designed to increase the octane rating of your fuel, as we found with the high octane fuel test, unless your engine has been tuned to take advantage of increased octane levels, octane boosters are unlikely to boost engine power output.
2 CHEMICAL ENERGY BOOSTERS
Petrol has a typical energy potential of about 46.7 megajoules per kg (around 35MJ/litre). The amount of heat released from combustion is proportional to how hard it can push on the piston. More energy = more push = more power.
These are designed to improve combustion and lower exhaust emissions. The most popular petrol oxygenate is ethanol. In fact, UK petrol contains at least 10% ethanol from the pumps. MTBE (Methyl Tertiary Butyl Ether) used to be the oxygenate of choice by petrol distillers, but ethanol is ‘green’ or something. Much like octane boosters, unless your engine is specifically designed for highly oxygenated fuel, power is likely to drop rather than increase.
If left for long enough, petrol can leave deposits as it evaporates. The worst place for this to happen is on injector nozzles and orifice plates. Special detergents and solvents can break down these deposits, helping to restore an injector’s ability to spray fuel in a nice even mist, rather than a miserable dribble.
Over time, petrol can absorb a certain amount of moisture and oxidise when exposed to air. This is the main reason insoluble deposits form in fuel systems. All pump petrol sold in the UK contains some percentage of stabilisers, which are designed to reduce this degrading process. But if you intend to leave your bike fuelled-up for a long period of time, consider splashing a bit more in for good measure.