I just purchased a 2014 Civic SI. In stock form does this car require premium fuel?

 

I have a R18. The stock NGK spark plugs are $15 each. Supposed to burn fuel more efficiently. But i can still use 87. Really just up to you. More octane = more power

 

So, do you think the "Premium Unleaded Fuel Only" signs on the instrument cluster and inside the gas filler neck door are SUGGESTIONS ??? Your engine has 11:1 compression... 87 Octane fuel is NOT recommended to run in that engine. The R18 powered Civic that 94 accord typeR owns does NOT have a performance engine and thus can function on lower octane fuel. Your car will KNOCK heavily on low octane fuel and the computer will reduce power to try and compensate for the poor fuel quality... however, engine damage can occur while the ECU tries to adapt and protect the engine. This process is not instant... it takes time for the ECU to learn that you have put the wrong gas in the tank. Following the manufacturers' recommendations is usually the best policy.

 

The K20Z3 will run on lower grade pump gas. It will also create a lot of problems for the owner if it is run in VTEC for a long time with lower octane gas. The 91 or higher octane reduces the chances of pre-detonation inside the cylinders due to heat soak when the K20Z3 engine is at high RPMs. The higher the octane rating, the less knock and ping you will get.

 

well now that changes everything

 

And the K24 is just as temperamental with its fuel grades. Just follow the writing on the fuel tank filler cap.