Spark plug Bosch W8DC for 518 from 07/1975 up (518 LHD 4625659 / 518 RHD 3820624) and for 518i+520/4+520i all years of manufacturing only for country version AUS, S, you need 4
Oregon 77-310-1 Spark Plug Replaces Bosch W8DC Champion N11yc Ngk Bp5es - China Oregon Stihl Gator Oregon 77-310-1 and Stens Chainsaw and Cut-off Saw Spark Plug