GO:0043430:   2-decaprenyl-6-methoxy-1,4-benzoquinone methyltransferase activity
Catalysis of the reaction: 2-decaprenyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-methionine = 2-decaprenyl-3-methyl-6-methoxy-1,4-benzoquinone + S-adenosyl-L-homocysteine.