Has acyl-CoA thioesterase activity towards long-chain (C16 and C18) fatty acyl-CoA substrates, with a preference for linoleoyl-CoA and other unsaturated long-chain fatty acid-CoA esters (PubMed:22586271). Plays an important role in mitochondrial fatty acid metabolism, and in remodeling of the mitochondrial lipid cardiolipin (PubMed:22586271). Required for normal mitochondrial function (PubMed:22586271). H2O + hexadecanoyl-CoA = CoA + H(+) + hexadecanoate (9Z,12Z)-octadecadienoyl-CoA + H2O = (9Z,12Z)-octadecadienoate + CoA + H(+) H2O + tetradecanoyl-CoA = CoA + H(+) + tetradecanoate (9Z)-octadecenoyl-CoA + H2O = (9Z)-octadecenoate + CoA + H(+) (9Z)-hexadecenoyl-CoA + H2O = (9Z)-hexadecenoate + CoA + H(+) (5Z,8Z,11Z,14Z)-eicosatetraenoyl-CoA + H2O = (5Z,8Z,11Z,14Z)-eicosatetraenoate + CoA + H(+) H2O + octadecanoyl-CoA = CoA + H(+) + octadecanoate Homodimer. Belongs to the THEM4/THEM5 thioesterase family.