Isomerization of polyisobutylene

A method of inhibiting and/or removing deposits in an direct injection engine, the method comprising:

• adding to the engine a detergent made by a reacting a polyisobutylene (PIB) with a compound having a polar moiety;
• wherein the polyisobutylene (PIB) has at least 50 mol % of PIB macromolecules that include a tri-PIB group;
• and
• wherein the compound having a polar moiety is selected from (a) a Mannich reaction product of a hydroxyaromatic compound, an aldehyde and an amine;
• (b) succinic anhydride having one or more hydroxyl and/or amino and/or amido and/or imido groups;
• (c) a mono- or polyamino group having up to 6 nitrogen atoms, of which at least one nitrogen atom has basic properties, (d) a quaternary ammonium salt of an amide or an ester, (e) a compound having nitro groups, optionally in combination with hydroxyl groups, (f) a compound having hydroxyl groups in combination with mono- or polyamino groups, in which at least one nitrogen atom has basic properties, (g) a compound having carboxyl groups or their alkali metal or their alkaline earth metal salts, (h) a compound having sulfonic acid groups or their alkali metal or alkaline earth metal salts, (i) a compound having polyoxy-C2- to -C4-alkylene groups which are terminated by hydroxyl groups, by mono- or polyamino groups in which at least one nitrogen atom has basic properties, or by carbamate groups, and (j) a compound having carboxylic ester groups.