As a general rule yes---compression and fuel rating go together. Turbocharged/supercharged engines use 91 fuel because the turbocharger increases the engine compression by about 1.4 times.
With traditional port fuel injection, for the most part it would need premium. In some cases (very retarded ignition and cam timing, small displacement engine, etc.) you can go higher on mid grade.
However, with direct injection, you can go much higher in compression without premium fuel. The new Mazda Skyactiv engines are as high as 13.5:1 compression and run on regular fuel.
Compression ratio does affect the grade of fuel required. But so do other things. Most modern cars can be driven with lower grade gas, but the computer will cut back on horsepower. So if you tend to drive easy, you can use the cheaper fuel, you just may not enjoy the potential of your car.
iT IS ABOUT COMBUSTION CHAMBER DESIGN AND THE PRECISION OF THE ignition AND injection SYSTEMS! tHE compression ratio AS USUALLY TESTED QUITE THOROUGHLY BEFORE THE CAR IS REleased FOR PUBLIC CONSUMPTION. sOME CARS WITH THIS HIGH A RATIO USE regular gas. READ YOUR FUEL FLAP DECAL! Most newer cars have KNOCK SENSORS which try to prevent knock and pre-ignition to save the ALLOY PISTONS from destruction! PLEASE INCLUDE the type of car you are asking about! Most EURO cars, e.g. use piezo-electric injectors, and variable VALVE LIFT as well as variable valve TIMING! You will not know how the compression ratio affects without thorough TESTING!
necessarily need premium fuel ? In other words- does the compression ratio determine whether you need premium fuel or not?
