I have a 1981 300D with 287k miles. It has a custom fuel heater sufficient for running straight veggie oil. I have run 6 full tanks of SVO and my Benz ran amazing with no clogged filters or any performance loss. My supplier did not have veggie when I came to fill up and filled me up with one full tank of biodiesel. After 280 miles on it I added 1 gallon of diesel and 5 gallons of veggie oil. The motor runs great but now my prefilter becomes clogged constantly with sediment from 32 years of dino diesel use. Just the one tank of biodiesel has created so much sediment from cleaning my fuel system, that the veggie can not even reach the prefilter due to large chunks in the fuel line. Is there any advice you can give me to make my car return to normal besides dropping and cleaning the tank?

Drain the tank and fill it again

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Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

better for the environment for you to replace the dino-tank 1x ...

i use 100 biodiesel mostly ... in my 1979 300SD. Not one issue (knock on wood) with filters = they're clean.

i transitioned to biodiesel ... 10%, 20%, 50%, 80% then 100%.

Go slow in transition to biodiesel like mentioned above.

I have always heard NOT to mix biodiesel and veg oil in the same tank, especially non-commercial grade/spec fuel or home brews! A poorly "washed" biodiesel may have excess chemicals like the methanol inside that will react with any veg oil in your tank and create partially converted compounds that are BAD.
I hesitate to even use biodiesel in a 2-tank system for the purge cycle.

Now it is well known biodiesel is a cleaner and will break loose tons of old material from our tanks of diesel or WVO. Be prepared with spares and comfortable changing filters on the road, if you are using either alternative fuels

IT is not that bad to pull the tank out of your trunk (i have done twice, not by choice)
Startron clean the tank,replace the decayed old copper screen with a fresh plastic one that won't brakdown so fast in WVO, replace all the rubber line sections, flush the hard lines with mineral spirits, new filters and go ahead to run purge cleaner through the engine.
Fresh tank of dilluted B100 and run her hard on the highways

Final recommendation: transition back to 100% dino diesel and then start you WVO again if using the stock tank. Avoid mixing biodiesel and veggie oil directly

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1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

My truck has used blends of VO, BD, ULSD and jetB for years.

Commercial grade spec biodiesel should be good as regular diesel.

I have thinned WVO with biodiesel from the big station's pumps before with no problems as well.

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1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

I have run several W123's on veggie oil unconverted. I mix a little gasoline with well filtered veggie oil and pour it in the tank and drive. This bypasses all the hassels with conversions that aren't done just so. Only works in weather above about 50 deg. F.

I have driven over 30 K Miles on one of them,, and over 10,000 on another.

EACH ONE SEEMED TO RUN FINE FOR 100O MILES OR MORE, THEN GO THRU A PERIOD OF FREQUENT CLOGGING OF THE PRE-FILTER.

I just drained the tank once or twice, put up with frequent filter cleaning for a few hundred miles, and gradually things improved to where I can now go pretty near a whole season without cleaning or replacing the pre filter.

Not sure if it was the little bit of gasoline, or the oil itself that dissolved stuff off the tank walls. I have never run biodiesel.

sun tort(o)ise


2-85 300D's
81 240D
81 vw rabbit diesel p.u.
newly acquired 80 300D wagon with ticking noise in engine