Filtering Used Vegetable Oil (or How I Spent My Saturday)

Maggie filtering veggie oilYa know those projects that you keep putting off for months and months because they sound intimidating and then when you finally get around to it, it ends up being quite easy? Well, that was my experience this weekend when I put together a little filtering system for my greasecar. As you may recall, I love my greasecar but find one of the biggest limitations is filtering the used vegetable oil. Used veggie oil is pretty gross and it’s pretty heavy. There’s also the catch that it’s very bad to get water in your veggie oil fuel so anything that is washed also has to be thoroughly dried. Anyway, I have considered building a really fancy filtration system and have lusted after electrical veggie oil pumps but so far can’t justify the cost, so I have been using cloth filter bags from They’re pretty cool but it has been challenging figuring out how to get the oil through them with a minimum mess. So after much deliberation, I built myself a little bucket filtration system!

Step one was cutting a hole in a bucket lid to accommodate the filter bag. Plastic buckets (and lids) actually cut pretty easily with a boxcutter although it took me awhile to figure out that it’s most efficient to just score the cut and then snap off the plastic rather than cut all the way through. (It also felt safer, as in less likely to cut off any of my fingers by accident.)

Filter bag in lidMaggie drillingStep two was drilling a hole in the bottom of the filter bag bucket. This is a two-bucket system, with the filter bag taking up the top bucket and the lower bucket storing the filtered oil. My goal was to let the veggie oil flow slowly into the lower storage bucket. I wasn’t sure how big to make the hole. I had brief flashbacks to my engineering hydrology classes at Purdue but decided to go with the trial-and-error method of hole-sizing, which meant starting small (it’s a lot easier to make it bigger).

Step three was cutting a larger hole in the lid of the bottom (storage) bucket. I wanted to make it big enough to let the oil drip cleanly through from the top bucket but small enough that the lid will still be able to support the weight of the top bucket even when it’s full of oil. I was amused to notice the recycling symbol on the bucket lid and realize that I can throw the plastic bits in with my recycling. Yay Bloomington Recycling!

Veggie Oil Close-UpBucket Lid with Recyclable signStep four was putting it together and testing it out. As you may have noticed, my jug of used vegetable oil sprung a leak at the bottom so I decided to “pour” it out of that end. I think the slow release was probably a good thing. The cloth filter bags are very effective but the flow rate is pretty slow, especially when the oil is cold. It was about 50 degrees out, which felt fantastically warm to me, but the oil was still a little thick. I hear that fancier folks have special veggie oil heaters to improve filtration rates. Maybe some day.

In the end, I managed to filter all 5 gallons of veggie oil with only a few minor spills. Then I poured the bucket of clean oil into the storage tank in my trunk, with a few more spills. Bleah. Alas, that one has to be chalked up to user error. I drove out to my aunt’s house last night but my engine never heated up enough to switch to veggie oil. I suspect there may be a problem with my thermostat since it never seems to heat up like it used to but that is another project. For now, I’m pretty happy with my new filtration system. It’s very satisfying to complete a little project and feel that I actually am a handy person. Next up? Figure out a way to decommission my dying water heater in a way that the landlord will HAVE to come fix it… this!

4 Responses so far »

  1. 1

    State of the (blog) union | said,

    May 16, 2008 @ 6:13 pm

    […] most popular articles have been about Maggie’s car (and the veggie oil it uses), making pizza, and doing laundry, followed by my number-crunching on getting […]

  2. 2

    Erik Sturm said,

    October 26, 2008 @ 12:42 am

    I really like this method I think I can wing it! What kind of filter should I use and where do I purchase them? Look forward to hearing from you soon. Can’t wait to produce my own recycled fuel since Costco raised their soybean oil to $25.00 for 5 gallons when it was only $13.00 a year ago.

    thanks again,


  3. 3

    Reece` said,

    June 19, 2012 @ 2:31 pm

    Is there a video of you making your fuel anywhere? Where are some places I could get oil from?

  4. 4

    Maggie said,

    June 20, 2012 @ 8:39 pm

    I’m afraid we didn’t capture any video of veggie oil filtering but honestly my system was never that great. You can get used vegetable oil from most restaurants (anyplace that deep fries anything). I’ve found locally owned restaurants to be the easiest to work with because you can figure out who the right person is and talk to them about how you need the oil to be stored. Good luck!

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