Dura Lube HL-40199-06-6PK Severe Fuel System Cleaner, 16-Ounce, 6-Pack Directions: add full contents to gas tank at least every 3,000 miles; treats up to 42 gallons, highly recommended for all direct injection and turbo engines. Severe formulation cleans the entire fuel delivery system and helps aid the phase separation occuring in fuel. Helps aid loss of fuel economy, poor accelertion, engine hesitation and knock