About a year after buying this 2001 Pontiac Bonneville SSEI - fuel injected V6 that uses premium fuel I weaned it for about 6 months by gradually mixing 1/2 premium with 1/2 tank mid-grade then mid-grade with regular. I assumed that this would reset the computer to accept regular instead of premium. Since 2002 and about 50,000 miles later I have not had any problems and no knocking or pinging. I have read that this will cause engine damage. Please tell me if this will damage the engine and what should I do to prevent any damage. Thanks, Bob