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biodiesel and the OM603

8045 Views 10 Replies 8 Participants Last post by  DSLVO
I've been interested in SVO, WVO, and biodiesel for some time now, but now that diesel is approaching $2.50+ per gallon, I'm starting to think more seriously about it. I had always considered a conversion kit to run SVO/WVO, but I'm too unwilling to give up space in the back of my 300TD for an extra fuel tank. (I think the greatest thing would be a tank that fit in the foot well for the 3rd seat, which I use for storage now anyway).

So I'm wondering if anyone has experience running biodiesel in their 124 diesels, particularly with the 603 engine as mine has. I've read considerably about people doing it with 123s, and some issues arise relating to fuel lines and filters (something about rubber?), so I was wondering what I should expect. B20 to start? B100 too much? Oh, and has anyone just put straight, clean veggie in their tanks, say to at most 15-20%?

It's cold here now, so I might have to wait a month, but I'm getting tired of these gas prices. Not that biodiesel is free, but if I'm going to pay so flippin' much for fuel, it might as well have all the environmental benefits of veggie. Plus I want the car to smell like <a href="" target="#">D's</a>.
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While I'm no expert on biodiesel, I have run it in a Dodge w/ a Cummins engine. At one point I was looking to find an old Benz (W123) for the purposes of conversion to biodiesel and did some research into it.

From my understanding the W123 diesels could burn just about anything: WVO, SVO, kerosene, biodiesel, and blends of most of these. The 123s have bulletproof engines with minimal pollution controls that make them perfect candidates for this application. I have heard about people pouring Wesson cooking oil directly into the tank on their 123 with no problems at all.

The 124 diesels have much more stringent pollution control devices, trap filters, etc., on their engines when compared to the 123s. From what I have read the 124 engine is not a good candidate for SVO or WVO applications. It's not that the engine can't burn it, it's that the emissions control system doesn't know what to do with it. You would probably be OK burning a biodiesel blend, but I would start out with a blend that is more "diesel" than "bio" and slowly acclimate your car to it. This will allow you to measure the performance as you slowly acclimate your engine to this new fuel source.

Some things to look out for with Biodiesel:

Biodiesel is made by splitting the oil molecules into their two main components: glycerine and esters. The glycerine is the "waste" product and you burn the esters.

The esters present in the biodiesel act as a natural cleaning agent inside your fuel delivery system. They will erode any sediment buildup in your tank and fuel lines and eventually cause your fuel filter to become clogged. You'll probably want to start out with a new fuel filter before switching to biodiesel, but expect it to become clogged as well eventually. I went through 3 filters in the Dodge before I stopped experiencing problems. You've been running on dino diesel for a while so I would expect to have to change the filter a few times. Although it can be a PITA to keep changing the filter, ultimately it is good for the engine as it cleans it up.**

Second is that the esters don't agree with some rubber/plastic compounds that are used in fuel lines, gaskets, etc. They will eventually break over time. This is more likely with a higher concentration of "bio" and less "dino" in the tank. You'd probably be OK with your existing components if you stayed with a 20% blend or less of "bio", but if you plan of running a higher concentration of "bio" (as I imagine you would), then you may eventually want to have these lines, gaskets, etc. replaced with a different compound that is resistant to esters.

If I were you then I would google biodiesel. There are a few good forums for users/consumers who are running it in their cars, and there is alot of good knowledge out there from people who have been running on it for years. I have a friend who converted her VW TDI to bio and hasn't had any problems yet.

** There is also another product on the market called AutoRx that uses esters for engine cleaning. They recommend a treatment cycle by adding it to your oil to help clean out engine sludge and they have had some really good results from it.
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I forgot to say to please keep us up to date if you decide to start running bio. The green aspect is very appealing to me and I'm sure others on this forum.

Since I couldn't find a European "gray market" 123 diesel w/ the ABS option, I have decided to start looking for a 124 (too many idiots cut me off on a daily basis around here that I am afraid I'd slam right into them w/o ABS). I was originally thinking about a diesel 124, but the added cost of diesel now cancels out the additional MPG you gain from it so I was leaning towards gas.
Thanks, Branshew, for your response. I appreciate many of your points. I have been looking at this for a while, and you sort of touch on some more ideas that are helping me solidify my approach. Besides the fact that there are so many more 123 diesels out there, they do seem to lend themselves better to running on veggie and consequently there are many SVO and bio 123's out there as oppossed to 124s.

But I have a 124, so that's what I'm working with. I think, because of the logistics, cost, and uncertainties, I can rule out running SVO/WVO and instead focus on running biodiesel. In this respect, my concerns really lie in the effects to rubber (if any?) componets in the fuel lines, and issues with the temperature at which the engine will run. For instance, I've read that when running bio, the injector timing should be backed off 2-3 degrees. This is something I have no familiarity with, but I guess it hinges on seeing where the temp guage goes after adding the juice.

The fuel filter is the other issue, which is fairly simple, but I'm not quite sure what we're looking at here. Is it the clear filter or the spin on that I should be watching?

I will keep the forum updated. Gas prices are getting too rediculous.
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I run my OM603 w124 300D on a 50/50 blend of Veg oil and diesel during the summer months and it runs better than it does on pure diesel.

Veg oil has more lubricant properties than pure diesel, so there are no problems with wear in the injector pump etc. It also runs quieter and there is no difference in fuel consumption. The only difference you can notice is the smell of the exhaust smells of spring rolls!

The OM603 will also run happily on 100% veg, but you would be better off getting some fuel line heaters installed to stop the veg oil getting more viscous in colder weather. As its more viscous that diesel, if you run 100% veg oil with no heaters you run a risk of incurring injector pump wear, as the pump is being made to work may also get sum gummed up injectors

Personally I do not like Bio Diesel as its a very astringent substance that can cause wear in injector pumps....saying that Benz/Bosch pumps cope with Bio Diesel better than many other manufacturers.

I would stick with pure Veg, or WVO.
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I had an 87 300SDL with the 603, and it loved b100 biodiesel and SVO. A fellow wagoner, I appreciate your desire to dodge the big tank that takes up the traditional trunk space. I have an 85 300TD that will be converted as soon as I'm able to collect all the parts again. Been really busy!

A friend of mine has had a few special tanks fabricated to work with w123 wagons, and I'm sure he'd do one for your w124 if you wanted. It fits opposite the spare tire, blocking the first aid kit door, but allowing the use of the 3rd seat. It's the best solution I've seen, and trust me, I've been looking! (I even considered a roof-top Thule box mounted tank, but not for very long...) is his website- you can tell him Kevin sent you if you're interested. Another guy I know is having a larger tank custom made for the same space, but it will be a larger volume, blocking part of the window. Not sure I'd go that route...

Now, the issues I had with the OM603 were few. I filled the tank with b100 and drove away. After about four tanks, I changed both fuel filters as a preventative measure. Neither looked strange. I also changed the injector return lines. Later, when I did the SVO conversion, I had to swap out most of the fuel lines in the engine bay to accomodate my two tank system. Unlike the 617, there is no manual primer pump, so I strongly suggest Miti-vacing the air out of the system rather than cranking and cranking to purge air. Once I was free of air, it ran great. Much quieter on bio or veggie than with petro diesel. Just don't overheat it!

I'd suggest against blending petrodiesel and SVO in your main tank. There have been several folks who've experienced a waxy precipitation with this blend. Go here for years worth of reading: Also some good reading on

P.S. where in the 'burgh are you? I'm originally from Monroeville, and there is a place in export (actaully closer to Delmont) that sells B100.

Good Luck!
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I think you will find that they have discussed this extensively on the diesel forum at

You can use the link below.
pure vegetable oil

i run my 95 E300D on nothing but vegetable oil new & waste

the car runs great and has 288,00 miles!
I was running my car on a blend of 70% WVO until I read some research papers done in Europe during the late eighties and early nineties that all said any blend of WVO greater than 50% would cause premature engine failure due to coking of injectors and gumming up the rings. I am now in the process of putting together a biodiesel processor so I can eliminate the source of the contamination, the glycerine.

Btw, as long as the rubber in your car is viton and not natural rubber, then the effects from the biodiesel won't affect that. Even if you have natural rubber components, the bio will cause them to start to weep, allowing you to replace them with the viton rubber replacement.
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