See the above website, it is not good for new car to use 91 or 93 gas, 87 is better. For old engine if there are carbon deposition and pre-fire happen (that means fire happens before the spark plug start to fire), 91 or 93 needed. But the purpose to use high octane gas is to avoid pre-fire which cause noise and block in engine, not to clean the engine.
The OCTANE RATING means block or ping inside the engine, caused by pre-fire due to above reason. Use 91 or 93 for good engine could cause incompletes combustion and lower fuel economy. Because it is more difficult to fire 93 or 91 than 87, especially for computer controlled fuel injection system of new cars, which is designed for #87 gas.
One of my colleague told me that he fills #93 once a month to clean his car, but the technical information from website indicated that this is impossible.
The OCTANE RATING means block or ping inside the engine, caused by pre-fire due to above reason. Use 91 or 93 for good engine could cause incompletes combustion and lower fuel economy. Because it is more difficult to fire 93 or 91 than 87, especially for computer controlled fuel injection system of new cars, which is designed for #87 gas.
One of my colleague told me that he fills #93 once a month to clean his car, but the technical information from website indicated that this is impossible.