The diffusion coefficientDand the thermal diffusion ratiokTfor dilute4Hein liquid3Heare calculated from Fermi liquid theory. The collision integral assumes a scattering amplitudea34expanded in scalar combinations of the quasiparticle momenta. AsT→0,Dvaries as1/TandkT/c,wherecis the concentration, approaches a constant. As shown previously, the limits forDTandkT/care determined by thermodynamic properties, the4Heeffective mass and partial volume, and properties of pure3He.We have decreasedkT/cby a few percent, by including the effect of∇Ton the3Hedistribution function. The temperature dependence ofDTandkT/cis linear and related to the coefficients in the expansion ofa34.Two coefficients can be found from thermodynamics. A conjecture about the remainder suggests thatDTmay have a maximum between 0 and 0.5 K. ©1997 American Institute of Physics.