Just for clarity, here is the section of the manual that states to not use fuel with octane boosters or specific additives that contain harmful and corrosive chemicals. Also, just as a note on my "Seafoam" treatment. I have only ran Seafoam ONE TIME. All other tanks have been without ANY additives or other chemicals, and have been REGULAR 87 octane. I have not seen, heard, or felt any side effects from the one-time use, other than noticeably less knock under load when running the 93 octane. But that is normal for any vehicle.