▁micro b ial ▁cont am ination ▁from ▁such ▁fu els ▁as ▁dies el , ▁red ▁dies el ▁and ▁b iod ies el . ▁This ▁fuel ▁cont am ination , ▁also ▁known ▁as ▁' f uel ▁bugs ', ▁or ▁' d ies el ▁bugs ', ▁or ▁' so - called ▁alg ae ' ▁build ▁up ▁over ▁time ▁in ▁stored ▁fu els ▁if ▁they ▁aren ' t ▁tested ▁and ▁treated ▁on ▁a ▁regular ▁basis . ▁F uel ▁Analysis ▁should ▁be ▁undert aken ▁before ▁fuel ▁pol ishing ▁is ▁comm enced ▁so ▁that ▁the ▁exact ▁cont am ination ▁problem ▁can ▁be ▁rect ified ▁with ▁a ▁target ed ▁solution . ▁A ▁second ▁fuel ▁test ▁should ▁be ▁performed ▁after ▁the ▁fuel ▁pol ishing ▁has ▁been ▁completed ▁to ▁confirm ▁the ▁problem ▁has ▁been ▁fixed . ▁ ▁S ources ▁of ▁cont am ination ▁▁ ▁Water ▁ ▁D iss ol ved ▁Water ▁ ▁Em uls ified ▁Water ▁ ▁Free ▁Water ▁ ▁Micro b ial ▁G row th ▁( AK A ▁Dies el ▁Bug ) ▁ ▁B acter ia ▁ ▁Ye ast ▁ ▁Mold ▁ ▁Bio - fil ms ▁ ▁Sol id ▁Part icle ▁Cont am ination ▁ ▁R ust ▁ ▁D irt ▁ ▁G ums ▁ ▁W ax ▁ ▁So ot ▁ ▁Organ ic ▁Comp ounds ▁ ▁Any ▁and ▁all ▁of ▁these ▁cont amin ants ▁will ▁eventually ▁lead ▁to ▁break ▁down s ▁or ▁engine ▁failure . ▁ ▁These ▁types ▁of ▁cont am ination ▁can ▁be ▁introduced ▁from ▁many ▁different ▁sources ▁throughout ▁the ▁supply ▁chain ▁of ▁the ▁dies el ▁fuel ▁as ▁well ▁as