Regular gasoline? Read the manual, look on the dash, look on the inside of gas cover.....it tells you what type of fuel to use. With 90k, you should just do the full 90k service as specified by the manual. You are given 30,k, 60k, and 90k. Take care of everything now and that way you can establish a baseline. CHEERS! and welcome to the forum.

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1990 190E 3.0L