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learn from my mistake: spare fuel filter first, biodiesel second

July 10, 2007

I knew better. I honestly knew better, but one piece of well-intentioned but contrary advice lured me in to not doing what I should have done. I really, honestly knew better, but got a case of the stupids.

I’ve been running my new-to-me Beetle on a biodiesel blend (approximately B45) for the past week. Up until last night I’d had no problems with the bio-Bug, when I had an unfortunate (but ultimately HIGHLY enlightening) experience. I was driving at highway speeds when I noticed a blip in engine power. It went away briefly, but returned, with the power fading quickly and speed dropping. I managed to get off the highway on to a side street, where it stopped and would not start. The culprit? Exactly what I suspected the instant power first dropped off: a clogged fuel filter.

It is well-known that biodiesel is a good solvent. It can remove oils and waxes from your laundry (remember that next time the lipstick ends up in the dryer), it can erode rubber fuel lines in older vehicles, and does a great job of cleaning the accumulated petrodiesel gunk out of your diesel fuel tank. The only problem with the latter is that said gunk gets caught by your fuel filter. That is exactly what it’s supposed to do, and saves you from a very expensive injector pump and/or injector replacement. Unfortunately, as the fuel filter catches this gunk, it will eventually clog and stop fuel from getting to your injector system. No fuel, no power, no driving. No fun at all.

I knew this. I’ve heard it repeatedly from many different sources. It is the gospel of biodiesel. I had even planned on heading this off right form the get-to, when I tried to buy a spare fuel filter at the same time I purchased my two biodiesel fuel gerry cans. However, someone I regard(ed) as quite experienced with alternative diesel fuels told me that it’s an old wife’s tale that gunk forms if you use petrodiesel; it only happens when you run on waste or straight vegetable oil. Surprised at this new take on the situation, but taking him at his word, I didn’t worry about it.

And now I’m paying (quite literally). The dealership has diagnosed and replaced a clogged fuel filter (a $30 part from any auto parts supply store – much, much, much more with diagnostics and dealership labour added in), and has made sure the injector pump is OK now that a new filter is installed.

PLEASE LEARN FROM MY MISTAKE!!! If ANYONE reading this is running ANY blend of biodiesel, or contemplating doing so, you MUST follow these steps IN ORDER:

1) Decide to run biodiesel in a diesel-powered vehicle or piece of equipment.
2) Purchase two (2) new fuel filters for your vehicle.
3) Learn how to replace the fuel filters, and replace the current one immediately.
4) Start using biodiesel or a biodiesel blend.
5) Be prepared to replace a fuel filter anywhere, anytime.
6) At the first sign of loss of power, replace the fuel filter again and purchase another new filter as soon as possible.
7) Repeat from step 5.

Following those step, in that order, will spare you from being inextricably stranded, being towed, swearing, inconvenience, paying car dealer shop rates, and a host of other things. I’ve made this mistake once, I will never, ever make that mistake again. Tonight I learn how to replace my fuel filter, and tomorrow I buy a spare one.

Updated Nov 13/07: I’ve since learned not to assume anything. While I stand by what I’ve written above, what I thought was a recurring filter issue turned out not to be. It wasn’t the biodiesel’s fault, after all.

6 Comments leave one →
  1. May 18, 2009 9:15 am

    Ive been using biofuels made from vegetable oils for seven years now and I can agree that the most important safeguard is a spare filter and the means to change it any time.
    One helpful device you can get is a small pre-heater for your fuel lines before the filter, this is ideal for cold weather runnning. I swear by these:
    Cheers for the article, I have printed it off many times to give to others.

  2. A. Fulton permalink
    August 22, 2009 9:14 am

    I installed a vacuum gague between the lift pump and the filter. The vacuum will increase before your engine stalls. Be aware of vacuum at different engine loading.

  3. colin permalink
    August 23, 2009 5:18 am

    Be very aware that many unscrupulous garages will do their utmost to try to swindle bio fuel users with unecessary repairs blamed on their fuel!
    Its usually just a simple fuel filter change or air lock or something similar!

  4. September 29, 2013 2:18 pm

    I only managed half a tank of Bio before i could only do 40 mph and about 1/2 miles before I had to keep stopping to let the Bio diesel trickle through my clogged filter! one filter later and i’m back in the game. Some say change the fuel filter after the first tank. mine only managed 50 miles!

  5. GeeForce1 permalink
    February 3, 2014 10:04 pm

    Allow me to reassure you it was nothing in the biodiesel that clogged your filter, but rather the solvent properties of biodiesel. Petroleum-based diesel contains sulfur as part of the fuel making process and bacteria love this. They colonize, grow and die, in the fuel. You take biodiesel with zero sulfur in it and pour it into your tank. A few hundred miles later, you have a clogged filter, not because of what’s in biodiesel, but rather what biodiesel does to the sludge accumulated from all that dead bacteria. Biodiesel has a property called lubricity, the ability to keep things from sticking. Now you have clumps of dead bacterial colonies being dislodged from the tank walls and put into suspension. This travels to the filter and now you have a clog. You will probably have to perform 3-4 filter changes before you see any abatement.


  1. more to learn about biodiesel « Andrew’s Sustainapedia

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