Catalyzes the hydrolysis of an acyl chain from the tetra- acylated cardiolipin (CL) and produces the tri-acylated monolysocardiolipin (MLCL) (PubMed:40903572). Prefers CL with shorter and saturated fatty acyl chains as substrates (PubMed:40903572). Together with Tafazzin (TAZ), it participates in the mechanism of CL remodeling, a process consisting of repetitive cycles of hydrolysis and reacylation of the fatty acids that make up CL, where the nascent acyl chains are replaced with longer, unsaturated chains (PubMed:40903572). . This is the function of Ensembl gene identifier ENSG00000164074 (ABHD18, abhydrolase domain containing 18).