High Octane Fuels

Octane is a measure of a fuel's ability to resist a phenomenon known as knocking, which a driver may detect as a pinging or knocking noise coming from the engine.  Knocking is the explosive or uncontrolled combustion of fuel in an engine’s combustion chamber that can very quickly destroy an engine.

The higher the fuel's octane number, the more resistant it will be to knock.

Higher-octane fuels allow engine manufacturers to design more powerful and fuel-efficient engines.

Australia's current standard fuel is 91 Research Octane Number (RON) unleaded and most cars sold here since 1986 were built to accept it. However, an increasing number of vehicles require 95 RON Premium fuel, while some high performance models require 98 RON fuel.

An engine's octane requirement can be found in the vehicle's handbook.  However, a fuel with a higher octane number than required will not necessarily produce noticeable benefits.

The only way to find out is to fill the tank with one of the premium fuels and try it, although such trials are somewhat subjective, being based on a 'seat of the pants' feel for the vehicle.

Here are a few things to consider:

  • Some engines will perform better on high-octane fuels while others will show no obvious benefit. 
  • The benefits for fuel injected vehicles depend on the sophistication of the car's engine management system. Systems that are capable of adapting fuel and spark maps to the fuel being used are most likely to show improved performance, while cars with less smart systems typically won't benefit.
  • Older vehicles with carburettors are unlikely to benefit unless they are specially tuned for it and even then any gains are likely to be limited.
  • High octane fuels may cause engines with very low compression ratios to run poorly. 
  • Anecdotal reports suggest that some cars produce better fuel consumption on premium fuels, although in most cases this alone is unlikely to offset the increased fuel costs.
  • Some premium fuels have a different additive package that aids in cleaning the fuel system.
Ultimately it is up to the user to determine if the benefits of using a premium fuel justifies the higher costs.

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