A 100Fe/3Cu/4K/16SiO(2) (w/w) catalyst (cf. D.B. Bukur et al., Ener. Fuels, 9, 620 (1995)), particle size < 53 mum, suspended in Albemarle's Durasyn-164 oil, activated 2 h/240degreesC with H-2, and tested 220 h at 260degreesC/1.5 MPa and 220 h at 260degreesC/2.2 MPa, converted CO in 84 and 80%, (H-2 + CO) in 79 and 76%, and showed selectivity toward C12+ 71.9 and 70.5%, resp. Activity loss, 2% in 260 h/1.5 MPa, rose considerably at 2.2 MPa. A novel activation procedure, with CO, enhanced catalyst activity and stability, esp. at 2.2 MPa. Within a 240-h test, conversion rose from 78 to 84%. The catalyst compared favorably with the Ruhrchemie, Mobil, and Rheinpreussen F-T catalysts and is now the best for producing paraffin waxes.