Try to get an oil that is NOT the newer "SM" standard. Try to get one that is the older "SL" standard instead. All the "SM"s say they also meet "SL", but they are NOT the same and they are NOT as good. They have reduced levels of ZDDP (zinc phosphate). I've noticed that Royal Purple synthetic is still "SL" but you better check to be sure. I'm running some old Amsoil that I have a stash of that is "SL" but I don't know if their new stuff still is.
Regards, Eric

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89 300E "Benzer1" 15.924 Uncorrected
93 400E "Benzer3" 14.200 U.C.
95 E420 "Benzer4"
92 300E "Benzer5" 16.299 U.C. Future turbo CNG
87 300D "Benzer7"
87 300D "Benzer8"
87 300D "Benzer9"
87 300D/70 AMC Javelin "Sidewinder-Benzer"
87 300TD "Benzer11"
06 E320 CDI "Benzer12"
05 E320 CDI "Benzer12A"
71 AMC Javelin AMX 401 "Sidewinder"
74 AMC Hornet 401 "C.K.10" 13.63 U.C.
74 Bricklin SV1 "Presto" AMC 360 pwrd.