What is the recommended gasoline grade for a 1991 Honda Civic LX?

Answer 1

87 Octane. Using a higher grade is a waste of money. The engine will perform no better and get no better mileage. The only time a higher grade is necessary is if the engine is experiencing pre-detonation, commonly called pinging, and you cannot otherwise cure the problem. As per the original manual you should use 91 Octane. Using lower octane will result in pinging and some time loss of power specially when climbing uphill. If you have high milage on the car I would recomend to use the 91 octane and go for a highway drive from time to time decarbonized the engine. 1991 Honda Civic LX needs manual valve adjustments that will make the engine run smoother and quiter. Loose valves are sometimes mistaken as pinging.