  We show that for almost every polynomial P(x,y) with complex coefficients,
the difference of the logarithmic Mahler measures of P(x,y) and P(x,x^n) can be
expanded in a type of formal series similar to an asymptotic power series
expansion in powers of 1/n. This generalizes a result of Boyd. We also show
that such an expansion is unique and provide a formula for its coefficients.
When P has algebraic coefficients, the coefficients in the expansion are linear
combinations of polylogarithms of algebraic numbers, with algebraic
coefficients.
