Can You Really Use Vegetable Oil to Fuel Your Car?

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.

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?

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.

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.