I have 98 Mitsubishi lancer and recently i swapped my old 1.3 engine for 1.5 engine because my old engine was worn out anyways the mechanic recommend using 20w50 mannol safari which is rated SN while other told me that SN isn't suitable for old engines and the maximum rating i could shoot for is SL " in egypt we have SF, SG, SJ, SL as i know in USA those ratings might be history " is this true that i can't or shouldn't use SN rated oil and what gives oil its rating SJ or SN or whatever