I think the split was 86 and 87. Our 1986 190e 2.3 does NOT require premium. My 1994 E320 does.

I am not sure if the premium requirement was across the entire model line up, but it may have been.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE