87 or 89 octane fuel

Hello,

The only reason at all to run higher octane rating gas [89, 91, 93 octane] then 87 octane is if you have a high compression engine or forced induction[turbo or supercharged]. Gas is gas is gas is gas. The octane rating of gasoline is there to tell you it's resistance to self detonation when compressed. Detonation is a condition where the air:fuel mixture that is usually detonated by the spark plug self ignites in the combustion chamber while the piston is still on it's upward travel of the compression stroke. It will make a loud "knock" from the flame front "slapping" the upward traveling piston and can be catastrophic for the engine's internal parts. Vehicle's today employ knock sensors and Engine Coolant Temperature Sensors that will retard the ignition timing when knock or higher engine temperatures are detected to take the engine away from detonation. Octane can be compressed 100% without detonating. Heptane cannot be compressed at all without self detonating. So 87 octane gas is gasoline with the compression ratio of 87 parts octane and 13 parts heptane. 89 octane is 89 parts octane, 11 parts heptane, and so on. Also, if you look at any gas pump there will be a sticker that looks like this R+MS/2 on it. This is how they determine the octane rating and it stands for Real World + Machine Shop divided by 2. They run the gas on a real world engine add it to an engine running in a machine shop and divide it by 2 to get an average of the octane rating. Running 89, 91, 93 octane gas will not give you better gas mileage, make your vehicle run better, or faster, it is just there if you need gas for your higher compression vehicles.

Thanks,
Alex
2CarPros