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Fucking search engines, live it, love it, USE it. Advantages of AVGAS It is made in batches controlled within rigid parameters and this has made it popular with engine tuners, as, unlike motor fuels (MOGAS) the fuel they used did not vary in its composition throughout the year. However the prime attraction of AVGAS has always been its ability to generate a little extra power compared to MOGAS. This is because of its higher octane rating, which is a measure of its ability to resist detonation. Up to a point, raising the compression ratio of an engine will produce greater power, all other things being optimised to suit. However, the greater the compression ratio, the greater the chance of detonation (also called pinging or pinking after the characteristic sound it makes in an engine), where the combustible air/fuel mixture explodes instead of burning. No engine can take detonation for any period of time and will fail in some manner from the simple blowing out of a head gasket to the catastrophic breaking of a piston, conrod or crankshaft. The simple equation has been: higher octane = higher compression possible without detonation = more power!
Disadvantages of AVGAS
Until fairly recently, the only disadvantages suffered by the users of AVGAS have been that it cost slightly more than for MOGAS (typically 85 c/L compared with 65 c/L). Most circuits have AVGAS supplies on site or brought in, though Rally and Off Road competitors have had to arrange to collect fuel from local airports. Even so, this has hardly been an issue. The high lead content in itself has little effect on the engine, save perhaps for spark plug fouling in poorly tuned engines. With the development of electronically controlled fuel systems in popular vehicles, and its increasing accessibility to the motor racing fraternity through after market computer systems, leaded fuels, and high-lead AVGAS in particular have become less popular as they render ineffective the exhaust mounted oxygen sensors used to measure engine tune in as little as 25-50 hours of running, compared to over 500 hours for unleaded fuels. However, this is basically an issue of cost, not technical merit.
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