The invention pertains to a heat transfer composition comprising: at least one fluorinated ether fluid free from functional groups (fluid (H)); from 0.01 to 5% wt with respect to fluid (H) of at least one solid nano-sized additive chosen among metal, metal oxide or carbonaceous material particles, having an average particle size of less than 2 000 nm (additive (N)); and from 0.1 to 10% wt with respect to fluid (H) of at least one functional (per)fluoropolyether comprising recurring units (R1), said recurring units comprising at least one ether linkage in the main chain and at least one fluorine atom (fluoropolyoxyalkene chain) and comprising at least one functional group (functional PFPE (F)).