Bio diesel conversion - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 05-24-2012, 02:25 PM Thread Starter
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Date registered: May 2012
Vehicle: 78 euro 300d
Location: seattle wa
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Bio diesel conversion

Hey I have a 1978 300d euro spec and am trying to do a biodiesel conversion. It seems the rubber is disolved or broken down by the biodiesel because of its solvent properties. What do I need to replace before doing the conversion? Does anyone have any helpful info on this conversion or experience they would like to share? Anything would be appreciated!
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post #2 of 4 (permalink) Old 06-23-2012, 01:25 AM
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Simply change out your fuel lines to fresh new ones. Same as you would if it were an old gas rather than diesel rig, (there's alcohol in gas now too, which is what's in the bio that eats at the old rubber lines. Diesel is not a solvent like gasoline, it lubricates - that's one big reason they are such durable motors.) Modern fuel lines are made to handle this. I've been running B-100 or B-99 in my 300TDT since I got it in '99, (some 150k miles ago.) Other than changing the fuel filters regularly (the bio D cleans out the gunk in your system - the alcohol at work, basically,) that's all I've done. Diesel is diesel. You'll love it! Starts and runs better, emissions through DEQ are better, and it smells WAY better! (And the politics are better...)

And I should emphasize - pack a couple extra filters, both primary and secondary. Whether you switch to the bio or not, but especially if you do. You'll likely see, (depending on the condition of your tank, i.e. has it sat a lot,) the clear little plastic filter fill with gunk after a tank or two of Bio - it's cleaning things out and getting ready to run better! And keep spares handy. I've had to change them at the road side as I wasn't checking it regularly - but that was in the early years when I had to buy Dino diesel as often as the Bio, (just an availability issue.) And I use a Sharpy to put a date on both filters when I change them... It was a daily driver until a few years ago, (hence, the 150k over a few years - and at the time I made a point to change the other, spin on that you can't see into, every six months - just to be on the safe side.)

Good for you! And too bad there aren't more posts here yet about Bio-diesel! (At least that I've come across - but I'm new-ish here.)

The TDT is my third diesel Benz - they are unstoppable!

Last edited by Racer pdX; 06-23-2012 at 01:45 AM.
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post #3 of 4 (permalink) Old 06-23-2012, 08:51 PM
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Vehicle: 1973 220D, 1988 300SEL, 1991 300TE
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I'm not sure that "improves" anything, except maybe the smell - it is simply a different fuel. We are talking about a B fuel here, such as B20, B80 or even B100 which is refined veggie oil. Basically they remove the glycerides in the refining process. The number after the B is the percent of fuel that comes from veggie oil.

Waste Veggie Oil (WVO) - unrefined - can be burned in a diesel engine that is warm already but you need to convert several things. You would need to have two tanks, one for regular fuel the other for the WVO and you need to start by using the regular fuel and once you have warmed the engine you switch to WVO - the you switch back before you turn off the engine. Often there is some kind of heater for the WVO.

I have run B fuels in my 1973 220D with no modifications (it does have new fuel lines as part of regular maintenance). I would not run WVO in my car - the big issue is the blow-by, the small amount of fuel and gas that escapes past the piston rings into the crankcase. If you burn WVO the blow-by will contain WVO. This will mix with your engine oil and in an engine as old as ours there could be a significant amount between oil changes. The WVO contains fats (those glycerides) which coagulate when it get cold and can block your oil flow when the engine is cold.

Good luck
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post #4 of 4 (permalink) Old 06-25-2012, 03:30 PM
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As for Veggie oil - also needs to be very well filtered before reaching your injectors.
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