Can any car be converted into a grease car?

Cars powered by vegetable oil are known as grease cars. See­ more pictures of alternative fuel vehicles.
Photo courtesy of California State Parks


­While most car owners are filling up on fossil fuels once a week, and hybrid-car owners are happily filling up a couple of times a month, people who have converted their cars to grease cars are laughing all the way to the bank.

The eco-bank, that is. Grease cars run almost entirely on waste vegetable oil -- that's the stuff McDonald's (and pretty much every other restaurant) dumps out of its fryers daily. Grease-car owners only have to fill up on diesel about every couple of months.

And while a grease car gets about the same mileage as a regular diesel car and requires an up-front investment that can take a while to recoup, the car's emissions levels are a marked improvement over other types of vehicles, making it a phenomenal tool for reducing pollution. For one thing, there's no sulfur in vegetable oil like there is in diesel fuel; and sulfur emissions, which cause acid rain, have been associated with increased cancer risk, too. Grease cars also release up to one-third fewer heart-and-lung-damaging particulates into the atmosphere.

­Other grease-car advantages target global warming. Greenhouse gas emissions can drop anywhere from 78 to 87 percent overall when you convert a diesel car to a grease car [source: Lloyd]. While they still emit nitrogen oxides and carbon monoxide, grease cars are carbon neutral: The vegetables grown to produce vegetable oil absorb more carbon dioxide than is emitted when a car burns that oil for energy.

So grease cars are a great choice for reducing your carbon footprint, but is it worth the effort? How hard is it to convert a diesel car into a grease car, and how much will it cost you?

In this article, we'll check out the grease-car process and find out if it's something just anybody can do. As it turns out, the initial conversion isn't such a big deal, but it's not the first step. The first step is to find yourself a good source of nasty fryer oil. You can't just drive up to a gas station and request fryer grease.

Converting a Car to Grease

Valentin Humer pumps his Mercedes full of recycled grape seed oil.
Valentin Humer pumps his Mercedes full of recycled grape seed oil.
AP Photo/Ben Margot

­ ­

Before you commit yourself to a carbon-neutral fuel source, you need to make sure you can actually get your hands on that fuel. While a grease car will still run on regular diesel, it's pointless to go through the conversion if you're just going to end up using regular fuel.

Most restaurants will have waste vegetable oil (WVO), and most will be happy to give it to you for nothing since they typically have to pay to dispose of it. The better the oil quality for cooking, the better it is for your engine, so start with the more expensive restaurants and caterers and work your way down from there. Just ask to speak to manager and see if you can take the oil off his or her hands. You can use the hydrogenated stuff you'll find at most fast food restaurants; it's just not ideal.

Once you know you've got an easy, nearby vegetable oil source, you can commit to driving a grease car. The first thing you need is a diesel vehicle (the conversion won't work with a gasoline engine). If you've got a diesel car or truck in your driveway, you're all set. Otherwise, you need to buy one. Buying a new one is slightly more complicated than buying a used one, because some states' emissions laws make diesel vehicles less common. Changes in the sulfur content of diesel fuel are starting to change this, though. In any case, getting your hands on a used diesel car is a cinch. Volkswagens and Mercedes have a lot of diesel vehicles out there, and many American carmakers make diesel versions of their pickups.

With a car on-hand, you're ready to convert it to a greaser. You can buy a conversion kit (about $1,000 to $1,500) at lots of online or brick-and-mortar retailers. The conversion basically alters the engine so it has an extra fuel tank and line and injector for the vegetable oil. The engine will take some diesel from the regular fuel line during start-up to get everything warmed up, as well as during shut down to flush the vegetable oil out of the engine. Otherwise, it uses the vegetable-oil fuel line. You can install the conversion kit yourself if you know cars, or pay about $1,000 for a mechanic to take care of it.

With the engine ready to run on grease, you're almost done. Owning the car requires some additional equipment and effort -- not the least of which is figuring out how to safely maintain a car that runs on a non-EPA-approved fuel source.

Owning a Greaser

French fries on wheels, or an environmentally sound fuel option?
French fries on wheels, or an environmentally sound fuel option?
Photo courtesy of California State Parks

Being a grease-car owner isn't quite like being the owner of a regular car. For one thing, you're going to be driving a car that smells like french fries. For another, you can't just drive up to a gas station to fill your tank. You become your own gas station, which requires some equipment.

First, you need some proper containers to transport the oil from the restaurant to your house and then store it at home. Since the Environmental Protection Agency (EPA) hasn't approved vegetable oil as a fuel source, you'll have to do some research to find out the best way to handle the stuff. Ask around to find out what other "greasers" use, consult some green-car experts, or find yourself a knowledgeable eco-mechanic to help you safely handle your new fuel source.

The other thing you need is a filtering system. The waste vegetable oil (WVO) from the restaurant has some food particles in it that need to be filtered out before you can gas up with it. You can take the oil to a shop that'll filter it for you, set up your own filtering system using strainers, heaters and oils drums, or buy one for about $700. Once you filter WVO, it becomes SVO, or straight vegetable oil. This is what the car actually runs on.

With your grease-car set-up all ready to go, you'll be driving around on used fryer grease in no time -- and filling up at the gas station almost never. People who average about 13,000 miles (20,921 kilometers) a year have to fill up with diesel only about six times annually, and the car gets about the same mileage it did as a diesel [source: Lloyd]. And while some people warn about extra engine wear because the engine wasn't initially built to run on vegetable oil, most people say they haven't seen any additional wear and tear at all. They just have to do regular maintenance like with any other car, except now they have to change the vegetable oil filter, too.

But will you have to worry about being turned in to the EPA when you go to do that maintenance at the shop? According to experts, there's not much to worry about in that regard. The EPA has yet to fine anyone for driving a greaser -- although you could get nabbed by the state for nonpayment of fuel taxes, so get yourself a fuel license if you go grease.

For more information on grease cars and related topics, look over the links on the next page.


Related HowStuffWorks Articles

More Great Links


  • "Frequently Asked Questions." Greasecar.
  • Galst, Liz. "Burger and fries to go." Salon. Aug. 13, 2008.
  • Lloyd, Robin. "'Grease cars' -- the answer to high gas prices?" MSNBC. Dec. 31, 2007.