there are various clear lines that will work at least partially with b100. that is, they may hold up for a few years, but not as long as viton would. not knowing anything about a 98 e300 i dont know how hard it is to change lines and if you would want to do that every few years. i have clear tygon lines on my 81 in places and its held up for over a year now. i do believe nylon is biodiesel rated, so if you can find clear nylon in your size that might be the way to go.

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1981 NA 300D 310k miles