How to Convert a Diesel to Use Vegetable Oil
Conversion Can Save Money, but It's Not for Everyone
Technically speaking, the kits don't convert cars. They allow cars to run on oil as well as diesel.
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Thousands of drivers have converted their cars and trucks to run on vegetable oil, the kind restaurants use to fry potatoes, chicken and egg rolls. These drivers discovered that the mixture of free fuel and clean emissions can taste might sweet.
Converting to vegetable oil is not for everyone. First, you must have a car that runs on diesel fuel. And it would help if you're handy with a wrench, or you'll have to pay someone to do the conversion.
There are other issues, too, but many people have made the switch and saved serious money on their fuel bills.
Why Do a Conversion?
Rudolf Diesel created his engine to run on diesel or any other fuel with a similar chemical structure, including oil from peanuts, palms and soybeans, among others. Diesel got his first patent back in 1892, but today's engines --- while improved in design --- have essentially the same characteristics as the original.
Sales of conversion kits spike every time gas and diesel prices take an upward jump, said Charles Anderson, owner of Golden Fuel Systems in Springfield, Missouri, a leading supplier of such kits. He recalls especially a period in 2008, when oil prices skyrocketed. "Everybody was freaking out," he said, "and we couldn't keep up."
An Internet search in July 2011 for conversion kits for cars yielded products ranging in price from under $1,000 to more than $1,500. Unless you're a decent mechanic, add a little extra for installation costs.
How quickly you can get that investment back depends on how many miles you drive and how much diesel fuel costs where you live. The average driver goes about 35 miles a day. At that rate, a diesel car owner might buy about 360 gallons a year. The U.S. Energy Information Administration says diesel fuel jumped from about $3 a gallon in 2009 to $4 a gallon --- just a little higher than regular unleaded gas --- in 2011.
At the latter price, converting to vegetable oil could save $1,400 a year. In other words, even average drivers will save enough money in less than a year to pay for the conversion kit.
How Does It Work?
Technically speaking, the kits don't convert cars. They allow cars to run on oil as well as diesel. That's important because at room temperature and especially in cold weather vegetable oil is too thick to make its way from the tank to the engine. A tiny amount of diesel fuel is needed to start the car and heat the vegetable oil until it's hot enough and thin enough to go through the tubes. A single diesel fill-up could be sufficient for an entire year.
Because of the thickness of vegetable oil, drivers using it must leave the motor running for about 20 seconds after they reach their destinations. It takes that long to reverse the flow and purge the engine of oil so that it won't be clogged the next time it is started.
It's best to start the conversion with a newer diesel engine, one without rubber seals. Vegetable oil makes such seals deteriorate over time, though rubber seals can be changed to seals that are not affected by vegetable oil
Then, you must install a second tank to hold the vegetable oil. Truck owners often put the second tank in the truck bed; car owners usually install it in the trunk or below the trunk, where the spare tire normally rests. A switch on the dashboard lets the driver select either the original diesel tank or the new one with vegetable oil.
Hoses from the radiator provide heat to the second tank via a heat exchanger, which makes the oil flow. The oil is then filtered and injected into the engine compartment.
Some conversion kit makers have improved the kits they sell. "When this started, we were using a lot of off-the-shelf components that we would modify," Anderson said. "Over the years, we've learned what works best and come up with a lot of new designs. Now pretty much all the major components are custom-made."
Pros and Cons
In addition to saving fuel, a conversion benefits the environment. Emissions from vegetable oil represent only a tiny fraction of those produced by the use of fossil fuels. The plants that yield the oil are renewable resources, mileage is not adversely affected, and the kits obviously provide a way to recycle oil used by restaurants.
Gathering oil can be messy, however, and it takes a little time, although it's possible to collect enough for a month or more at one stop. The oil must be filtered before it goes in a storage container and then again by the car's own fuel filter. The better you filter it before you put it in your tank, the longer the car filter will last.
Adding a conversion kit probably will void the part of your car's warranty that relates to the fuel system. If the warranty has expired, that wouldn't matter.
The debate about whether running on vegetable oil is good or bad for an engine continues. Some studies suggest it will reduce an engine's lifespan, while others claim the switch has tripled engine life.
You might think that the Environmental Protection Agency would send a gold star to anyone whose car or truck has been converted, but officially, vegetable oil is not an approved fuel, and those who use it may be fined.
That shouldn't stop you, said Anderson. While it is true that straight vegetable oil isn't EPA-approved, he said, "Neither is sunshine, water or butterfly wings. If you had a car that ran on water, it would not be EPA-approved," adding, "Now what's on the books and whether anybody has ever gotten their hands slapped are two different things."
Anderson said he has never heard of a single instance in which the owner of a converted car has received a fine. Besides, he pointed out, even after the kit is installed, the car is still able to run on diesel fuel, which is approved by the EPA.
- Photo Credit Ryan McVay/Photodisc/Getty Images
