Originally posted by pstephens46
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91/96
100/130
115/145
Were the grades that I have been familiar with in my lifetime. Back in my Navy days there were many big radial piston engines needing the 115/145 stuff. A tanker truck with possibly a thousand gallon tank would come around after each flight and hand the nozzle up so that oil, yes oil, could be added. Some of the oil tanks (one per motor) held about fifty gallons.
First number is the lean mixture rating and the second number is the rich mixture number. Aircraft motors have a means of leaning and richening the fuel/air mixture that the carburetors provides to the motor. So you can see the effect that using a rich mixture has on preventing detonation.
Oh, and some used water or water/alcohol that got sprayed into the intake manifold to help cool the air and prevent detonation. There could be a lot going on with multiple speed blowers, propeller controls, cowl flap controls, mixture controls, throttle controls, etc., particularly if there were four sets, one for each motor. The young pilots today don't know how good they got it made.
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