Plastic cleaning method using dispersant copolymer

A plastic cleaning method for cleaning a plastic article in an automatic dishwashing machine, comprising:

• selecting an automatic dishwashing composition for cleaning plastic, wherein the automatic dishwashing composition, comprises:
• a builder, wherein the builder includes a mixture of at least one carbonate and at least one citrate;
• a phosphonate;
• a nonionic surfactant;
• and
• a dispersant polymer comprising:
• (a) 85 to 91 wt % of structural units of formula I
• wherein each R1 is independently selected from a hydrogen and a —CH3 group;
• and
• (b) 9 to 15 wt % of structural units of formula II
• wherein each R2 is independently selected from an alkyl group with at least 4 carbon atoms and wherein each R3 is independently selected from a hydrogen and a methyl group;
• providing a plastic article, wherein the plastic article includes a polystyrene tumbler;
• and,
• applying the automatic dishwashing composition to the plastic article.