Been doing some more reading, and I've come across more than a few threads on other forums that seem to think that this is a bad idea. Something about biodiesel having more aromatics causes seals inside of the injection pump to swell, and ULSD, which has less aromatics, causes seals inside the injection pump to shrink...

Any truth to this? I ask because its a hike to get biodiesel, and I can only get a full tank 2-3 times a month, the rest of the time I run ULSD, so I will be switching pretty constantly.

Thanks for your input!

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1985 300D (CA, 173K)

Dynamite Biodiesel Co-op, Phoenix,AZ

I am assuming that when you fill up with bio, it is B100...

I don't think that using B100 only 3 or 4 times a month will cause any detrimental effects on your fuel system. You might want to keep check on your primary filter (the clear one) to be sure it isn't clogging. If so, you will need to change your filters. Bio is known to clean out fuel tanks, etc.

I haven't heard about swelling or shrinking IP seals, but don't think that would be an issue except for those that use B100 all the time. Viton seals are available if you wanted to change them out.

I'm sure someone with more knowledge will chime in soon...

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1987 300DT
2002 Ford F-250 7.3 Crew Cab Short Bed

Yep, I mean B99.

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1985 300D (CA, 173K)

Dynamite Biodiesel Co-op, Phoenix,AZ

The degradation of sealing surfaces is quite a slow process in any case. You may find that your filters plug up somewhat quicker than they would with ULSD , the solvent action of bio will clean out your tank and lines whenever you use it. I have not had any leaking IP seals in a steady diet of B100 for 5 years. Switching fuels should delay leakage if it was going to occur at all. Cheers Dan

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It's always something simple
91 300D 603.960 (from japan) 194K
92 Toyota Diesel Landcruiser HDJ81-t 116K
02 Golf TDI new head courtesy of PO
87 300D
97 BMW 525 TDS Wagon 5spd
bunch of Onan and other diesel generators

It's not going to hurt anything. Think of it as filling up your tank every so often with a mild fuel system cleaner. Over the last 6 years I've run straight diesel, straight Bio, and all kind of blends. I've never experienced any issues. It's not going to do anything. Your fuel lines will eventually breakdown no matter what fuel type you use. Some may cause it to break down a little sooner than others. The injection pumps on the 617's rarely leak. VW's are much more prone to that. Just keep an eye on the fuel lines each time you change the oil, and some day you may notice them starting to get soft or leaking. Then it's time to change them.

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I generally switch back to D#2 for a period of time every year, at least enough tank fulls to make sure all the bio has been flushed out. I've only been running B99 for 3-4 years, but I've had no leaks so far. At this point, even if I do have leaks in the future, I can't really lay the blame at a switch, no matter the timing.

I think its certainly possible, but its also a YMMV thing.

Now water pumps, that's a differen t story. I've been running D#2 all winter long this year, and now she's gone and blown a water pump gasket as soon as the weather warmmed up. Clearest case of failure due to D#2 I've ever seen

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

Heck no. Were they scientific studies or part of our new "DIS-infornmation age"? Must be careul about millions of armchair engineers out there.

I swtiched between them all the time, and go full D2 in Buffalo winters. All I can say, is that mixing them in the tank causes stratification, i.e, they dont mix well.

Seals inside an injection pump, really? Only ones I know about are on top, under the DV.

I suspect that the information you've received may be incorrect. Biodiesel converts triglycerides (a molecule with 3 esters, each with a fatty-acid tail -- therefore NON-aromatic hydrocarbons) into mono-alkyl esters. These do not contain aromatic ring structures.

Petrodiesel, on the other hand, contains up to 25% aromatic hydrocarbons.

If anything, aromatics are typically more reactive. Benzene, for example, is a known carcinogen.

http://en.wikipedia.org/wiki/Biodiesel_production
(I know wikipedia isn't exactly scientific. I can cite a more scientific reference if need be.)

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-1985 300TD - 324k mi on chassis. MB "Tauschaggregat" 617 motor + 4-speed conversion
Alaska Roadtrip 2009
-2002 E320 Wagon - 197k mi
-1998 E320 Wagon - 310k mi - retired

"DIS-information" age indeed.

1. Viton
2. Viton
3. Viton

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RIP:
2011 E350 BlueTEC, Schwartz 81k (totaled by uninsured drunk driver)
1964 Unimog 404.1 (wrongfully towed by the city)
1994 E320, Brilliantsilber 208k (transmission shuffled off after sudden catastrophic fluid loss)
1982 300D, Silberblau under a blue repaint 256k (sold for parts)
1995 E320 Polarweiss, 131k (sold for parts)
1995 E300D Polarweiss, 287k (totaled by drunk driver)

Just so you know this issue is real for non-viton seals. You described the problem perfectly, the issue is seals shrink when you go cold turkey from B99 and switch for months on dino. (not one tank.) The good news is that I have yet to see where this is an issue with my wife's 300D but I have never gone 'cold turkey' for months on Dino. I did with my 2003 Jetta a few years ago, and the bottom and top seal on injector pump started leaking. The Mercedes seem to use less seals and more gaskets between flush parts and these don't seem to leak - ever. Just keep an eye out on things. First order of business is to replace all fuel line hoses in the engine compartment & underside (3 bits of hose) with SAE30R9 5/16" and viton return lines.

Viton

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'84 300SD sold
124.128