GO:0008425:   2-polyprenyl-6-methoxy-1,4-benzoquinone methyltransferase activity
Catalysis of the reaction: 2-polyprenyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-methionine = 2-polyprenyl-3-methyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-homocysteine.