The present invention provides a drilling fluid comprising a compound c) which comprises a dimer and/or trimer fatty acid residue and an alkyleneoxy chain comprising a first ethyleneoxy section, a second ethyleneoxy section and a propyleneoxy section located between said first and second ethyleneoxy sections, wherein the propyleneoxy section comprises from 1 to 20 propyleneoxy groups. Use of such a drilling fluid to lubricate a drill bit, and a method of drilling a well bore comprising circulating such a drilling fluid, are also provided.