Can You Really Use Vegetable Oil to Fuel Your Car?

By: Ed Grabianowski & Kristen Hall-Geisler  | 

vegetable oil fuel
Is vegetable oil really a good alternative source for fuel? thieury/Shutterstock

It would be nice if we could find a new kind of fuel to power our cars — something that gives us good mileage and doesn't cost much. What if we could use some common and easily available substance for fuel? What if we can use a substance that no one really wants?

Free fuel would be great, if we could get it. Incredibly, that's exactly what some people are getting by using vegetable oil in their cars. Most restaurants just throw the stuff away when they're finished cooking with it, so some people have deals with their local eateries to periodically pick up batches of old oil.

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Of course there's a catch: You can't just dump vegetable oil into your car's tank and drive off into the sunset. You'll ruin your engine. However, with a few tweaks, you can make it work. To learn how you can fill up your gas tank with last night's chicken grease, we must first learn to distinguish between vegetable oils used as fuels and biodiesel.

Biodiesel is a type of fuel derived from vegetable sources, often soy, but it is refined at a special facility that must follow antipollution laws and other fuel regulations. Many vehicles with diesel engines can run on biodiesel or a blend of biodiesel and petroleum diesel without much modification [source: National Biodiesel Board].

Using vegetable oil to fuel a vehicle is an entirely different matter. You're basically using the vegetable oil you can buy at the supermarket (or get for free from a restaurant) as fuel. It's more of a do-it-yourself type of alternative fuel. There's no refining process and it isn't regulated or tested according to environmental laws.

In fact, using vegetable oil as fuel could be illegal in some states, as state and federal revenue agents in the U.S. require special licenses to drive converted cars, as well as payment of motor fuel taxes. Vegetable oil also isn't considered a great fuel source for long-term use [source: U.S. Department of Energy].

How do we actually use vegetable oil to power our cars? We'll discuss that next.

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Using Vegetable Oil As Fuel

How exactly do you use vegetable oil as fuel? First, you must have a diesel engine. The spark ignition used in a standard gasoline-powered engine would have a very hard time achieving combustion with vegetable oil. The fuel lines and pumps in a gas engine aren't intended to handle this type of fuel, and many of the sensors used to determine fuel ratios in modern cars simply can't cope well with this variation.

Assuming you have a diesel engine, you could use vegetable oil with no other modifications. However, vegetable oil has very high viscosity. It's so thick that the engine has a hard time atomizing the fuel completely when it is sprayed into the combustion chamber. The result is unburned fuel that clogs the engine.

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There are several solutions to this problem. The first is to mix the vegetable oil with more conventional fuels, such as petroleum diesel. This lessens the clogging problem but doesn't completely remove it.

Another solution is a two-tank system that uses petroleum diesel to start and shut down the engine. This heats up the engine on start up and flushes the veggie oil out of the engine before you shut it off. The veggie oil in the other tank is heated, since warmer vegetable oil can be atomized more effectively. In fact, vegetable oil is often solid at room temperature, so it needs to be heated to work at all. However, this still isn't the total solution.

To effectively use vegetable oil as fuel, some significant engine modifications are required. That includes first installing some new fuel injector nozzles with extensive filtering systems to make sure only clean fuel gets into the combustion chamber. Those who use dirty cooking oil from restaurants must run the oil through several filters before they can pour it in their gas tank. Any fine, durable fabric can be used as a filter to keep out bits and pieces of food or other contaminants that could clog fuel lines.

New glow plugs, used to ignite the fuel in cold start conditions, can also improve performance if they are designed specifically for use with vegetable oil. Additional heating of the fuel can be accomplished by placing engine coolant lines in contact with fuel lines. The hot coolant will reduce the vegetable oil's viscosity.

Several companies produce kits that include everything needed to perform this modification. They range in price from a few hundred dollars to almost $3,000, not including installation. The ANC Elsbett Company produces engines designed specifically to run on vegetable oil, although the company also performs engine conversions.

Vegetable oil is a very green way to fuel our cars, but will using it actually save us any green?

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Is Vegetable Oil Worth the Cost?

vegetable oil fuel
The amount of cooking oil discarded by restaurants every day is nothing compared to the millions of barrels of fuel Americans consume every day. fluxfoto/Getty Images

We know that some engines can really run on vegetable oil, but is it worth the effort? In terms of financial value, it's almost certainly not. The cost of the engine conversion will be very difficult to recover in fuel savings. On top of that, the cost of vegetable oil is approximately the same as diesel fuel.

Veggie oil might be cheaper depending on where you live or whether you can buy it in bulk from somewhere like a restaurant supply store, but it generally doesn't represent a major cost savings over petroleum-based fuels.

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What about all that talk of getting used vegetable oil for free from restaurants? If you can get your fuel for free, wouldn't that represent a huge savings? It would — for now. Veggie oil is used as fuel by a relatively small number of hobbyists who like tinkering with their engines and adjusting their vehicle's fuel ratios.

But make no mistake: The amount of cooking oil discarded by restaurants every day may seem like a lot, but it's nothing compared to the millions of barrels of fuel Americans consume every day [source: Energy Information Administration]. There's no way used vegetable oil could ever become the primary way we fuel our vehicles, and there's even less chance it would ever remain free.

Unfortunately, there's really no way to save money by running on vegetable oil, but there might be other reasons to use it. There are no widespread statistics available for veggie oil mileage rates, but in Consumer Reports' own tests, a car running on biodiesel produced slightly less pollution than the same car running on conventional diesel, but it achieved slightly fewer miles per gallon.

In light of these minor benefits, converting all vehicles to run on vegetable oil sounds less like a great deal.

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Originally Published: Sep 3, 2008

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More Great Links

  • Addison, Keith. Journeytoforever.org. "Straight vegetable oil as diesel fuel." http://journeytoforever.org/biodiesel_svo.html (8/24/2008)
  • Consumer Reports. "Fueling the Future." March 2013. (Nov. 11, 2021) https://www.consumerreports.org/cro/2010/05/fueling-the-future/index.htm
  • Energy Information Administration. "U.S. Product Supplied for Crude Oil and Petroleum Products." (8/23/08) http://tonto.eia.doe.gov/dnav/pet/pet_cons_psup_dc_nus_mbblpd_a.htm
  • Energy Information Administration. "U.S. petroleum products consumption by source and sector, 2020." (Nov. 11, 2021) https://www.eia.gov/totalenergy/data/monthly/pdf/flow/petroleum_spaghetti_2020.pdf
  • Freeman, Huey. "State makes big fuss over local couple's vegetable oil car fuel." Decatur (Ill.) Herald and Review. March 1, 2007. (8/25/08) http://www.herald-review.com/articles/2007/03/01/news/local_news/1021491.txt
  • Henderson, Bruce. "Driver ticketed for using biofuel." The (Charlotte, N.C.) News and Observer. July 11, 2007. (8/25/08) http://www.newsobserver.com/news/story/599471.html
  • Lee, Margaret Juhae. "Green Cars." National Geographic. July 2005. (8/23/08) http://science.nationalgeographic.com/science/environment/alternative-energy/green-cars.html
  • National Biodiesel Board. Biodiesel Basics." http://www.biodiesel.org/resources/biodiesel_basics/
  • Tickell, Joshua, et al. "From the Fryer to the Fuel Tank: The Complete Guide to Using Vegetable Oil as an Alternative Fuel." Biodiesel America, 2000.
  • US Department of Energy. "Straight Vegetable Oil as a Diesel Fuel?" January 2014. https://afdc.energy.gov/files/u/publication/54762.pdf

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