It is probably set up for regular 87 fuel.Let me explain octane.... The octane number of the gas is referring to the stability and temperature of ignition. Basically the higher the Octane Number, the more stable the gas and the higher the ignition temperature point. (91 octane ignites at a higher temperature than 87, which allows for more energy extraction from the fuel, if used in the proper engine with the proper set up.) The compression ratio refers to how much the air/fuel mixture is compressed in the cylinder before the spark plug ignites it, the more you compress the air/fuel mix, the more energy you can gather from the fuel...but more compression means more heat....(as a result higher compression engines run much hotter than lower compression engines), and lower octane fuel (which ignites at a lower temperature) will tend to ignite prematurely (which is called detonation), detonation is really bad, you can blow up your engine if you detonate, fortunately modern engines and modern fuels are designed to prevent this. Basically, higher compression means higher octane is needed. Forced induction (turbo and supercharged) engines also require higher octane fuels, for similar reasons, (a turbo forces air into an engine which causes the air to get hotter, therefore requiring a fuel which ignites at a hotter temperature (Higher octane). A supercharger essentially accomplishes the same goal as a turbo, but in a different way, with different dynamics.With Nitrous Oxide, you also need to use higher octane fuels for much different reasons than turbo, supercharge, and high compression. I will explain.... first you need to understand that an engine needs 3 elements to cause a combustion, 1. The fuel, 2. the air (specifically Oxygen), and 3. the spark to ignite the other two. An engine while running is in one of three states, 1. Lean : meaning that the engine has too much air (oxygen) and not enough fuel, 2. Rich: meaning that the engine has too much fuel and not enough air (oxygen), and 3. stoichimetric: meaning that the engine is running perfectly, with a perfect Air/ Fuel Ratio. Nitrous Oxide is an oxidizer, meaning that it increases the oxygen content of air, When you inject nitrous oxide into an engine you increase the Oxygen content of the air in the engine, (oxygen is the element in the air that is actually used) More oxygen in the air will make your engine run leaner which will cause the engine to run hotter because there will be less fuel (fuel has a "cooling effect" in an engine) therefore needing higher octane.So to recap: High compression, Turbo, Supercharged, and Nitrous oxide injected engines require higher octane fuels, and the higher octane (to a point) you use, the more Horsepower you will gain. In regular engines (unless specified) regular gas will work, but in some cases higher octane gas will provide a added performance boost, such as really old engines that have considerable carbon build up, and in driving in very Hot climate zones.Hope this helps..... I went on for a while......and i didn't even scratch the surface......Remember to choose best answer.>>Nunoyvg.... IS INCORRECT... NOT ALL HONDAS TAKE 87..... CERTAIN PERFORMANCE MODELS REQUIRE PREMIEM 91 OR 93. SUCH AS THE S2000, PRELUDE, DEL SOL W/ B16A MOTOR, CIVIC SI, AND SEVERAL OTHERS, USING FUEL THAT IS TOO LOW IN OCTANE CAN SERIOUSLY DAMAGE YOUR ENGINE, THAT GOES FOR ALL MAKES AND MODELS, GOING TOO LOW IN OCTANE IS MUCH WORSE THAN GOING TOO HIGH!!, IT IS REALLY DIFFICULT TO GO TOO HIGH, IT IS VERY EASY TO GO TOO LOW.