Oil company advertising has led many consumers to conclude that such premium fuel will make their car start more easily, get better mileage, and last longer. Oil industry officials acknowledge, however, that only vehicles with high-performance engines (less than ten percent of the market) actually benefit from high-octane fuel. The Federal Trade Commission has been challenging this practice for some time, but consumers still continue to purchase high-octane fuel at levels far above what is beneficial for most vehicles.