I have used B99 biodiesel in three different Mercedes for a period of about 7 years.

The first car was a 1979 W116 300SD. I bought the Parker hose that is sold as "biodiesel compatible" with the plastic lining in it, purchased from a popular Mercedes parts source. I found that it would get gooey in only a week or two and would start melting at the hose clamps. Pretty soon the hose would dissolve and leak, causing me to have to replace it. It seemed that the rubber part of the hose was not biodiesel-compatible, and that the plastic lining was all that was protecting it. When changing fuel filters, if any biodiesel got on the outer hose, it would melt it. I used Viton injector return lines, which worked, but were prone to splitting and didn't seal very well.

The next car was a 1968 W110 200D. I used the Parker lined hose again. Same issue, any biodiesel that got on the rubber part of the hose would cause it to become gooey.

Finally, I am driving a 1980 W116 300SD. It still has the old natural rubber hoses. The cigar hose is hardened and most of the hoses have the Mercedes logo on them. I started using B99 in it 4 years ago. I planned to replace all of the hoses, but kept putting it off, and after 4 years, I am still running B99 with every tank and still have all the old rubber hoses installed. But, here is what is interesting: none of the hoses are leaking! None of them have become gooey or melted, even after being soaked in biodiesel when changing filters. In fact, the factory rubber hoses are outperforming the "biodiesel-compatible" hoses. What gives?

I am starting to wonder if I should even use "biodiesel-compatible" hose.

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DON'T MESS WITH MY MERCEDES!


1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Highly Optioned, 350,000+ Miles