The thermodynamic stability of boundary lubricant films based upon mixtures of liquid perfluoropolyethers (PFPEs) is reported. Mixtures of A20H-2000 with Zdols 2000, 2500, and 4000 and Zdol-TX 2200 on amorphous carbon nitride films are investigated. An optical surface analyzer is used to image the autophobic dewetting of the mixture PFPE films. The critical dewetting thickness coincides with the monolayer thickness of the adsorbed mixture PFPE films as determined by the changes in the surface energy as a function of lubricant film thickness. The critical dewetting thickness varies linearly with mixture concentration. (c) 2007 Elsevier Inc. All rights reserved.