380 SE, SEL W126 09/1983 - 08/1985 M116.961,963. 380 SEC W126 10/1981 - 07/1985 M116.963. 500 SE, SEL W126 12/1979 - 08/1985 M117.961,963. 500 SEC W126 10/1981 - 08/1985 M117.963. This is probably because of modern fuel additives & the introduction of ethanol into fuel.
