All vehicles sold in the U.S. with gasoline engines are designed to operate on lead-free fuel. The minimum octane rating required by the vehicles covered in this guide is 87; however, using 91 octane is suggested. Because the fuel and ignition system is adaptive, the use of 87 octane fuel can be used, although some loss of optimum performance may be noticed. The preferred octane ratings can vary from model to model and may change during a vehicle production run. The manufacturer provides specific information for each model on the inside of the fuel filler door or on the door jamb. Leaded gasoline must NEVER be used, as it will damage the catalytic converter.
Although no specific interval is suggested by the manufacturer, both Audi and Volkswagen offer an approved fuel injector cleaner that helps to minimize deposits within the fuel system. As a preventative maintenance measure, use the fuel system treatment twice a year, most preferably before and after the winter months, and just before the vehicle is due for an oil change.