B-12 Chemtool June 4, 2013 Solutions Central › Category: Fuel Additives / Treatments › B-12 Chemtool 0 Vote Up Vote Down fred cub asked 11 years ago Should B-12 Chemtool be added before or after a refill ? fred 1 Answers 0 Vote Up Vote Down chemtooler Staff answered 11 years ago Add to tank immediately before refueling, to aid and dispersing of product. Please login or Register to submit your answer Username or Email Address Password Remember Me