Whats the point of filling a car with premium-grade gasoline?
–F.K., Berwyn A. Nearly all cars since the 1990s run fine on regular-grade 87-octane gasoline. Using regular-grade gas in high-performance cars with a high compression ratio such as a Chevrolet Corvette once was likely to cause expensive engine damage. But nearly all cars since the 1990s run fine on regular-grade fuel. Even those with higher compression ratios can safely use regular-grade fuel because of such things as fuel injection (instead of carburetors) and electronic controls that protect engines from a condition called “knocking.” That was a rattling sound that was the result of out-of-control combustion, with the air-fuel mixture an engine uses burning erratically. Such combustion could severely damage an engine. But using a lower-grade fuel than recommended by an automaker results in a loss in performance because the engine then doesn’t generate its full amount of horsepower. Q. I hear you could get more fuel per dollar by filling a vehicle’s gas tank early in the morning. Is
