Case study in converting a diesel auto to run on vegetable oil
Introduction and Fuel Types
Now that gas prices have gone through the roof again folks are going to be hearing a lot about alternative fuels and automotive advancements that save gas. While a lot of attention has been given to new and exotic technologies like hydrogen powered cars and hybrid electric vehicles, a simpler and more time-tested solution exists in the form of biodiesel and vegetable oil fuels. Instead of expensive new technologies, the trusty diesel engine, running domestically grown bio-fuels and/or used cooking oil, is suddenly being rediscovered as a viable alternative.
On this page, you'll learn more about biodiesel, and about the process of converting a used Mercedes Benz diesel to run on vegetable oil, in this case Waste Vegetable Oil (WVO), collected from the fryers in regular restaurants. The process described in this article, and much of its content, was inspired by another article written by Lyle Pearl of Santa Fe, NM. You can also download and read Lyle's original article in PDF format to supplement this article.
Before we begin with our discussion of biodiesel conversions, it's important to understand the different types of fuels that can be used in a diesel engine. There are three basic types:
||Petroleum Diesel - Petroleum diesel is refined from petroleum for specific use in diesel engines. This is the diesel you find at your local gas station or truck stop. Because it comes from petroleum, it produces carbon dioxide, pollution, particulates and sulfur emissions and increases reliance on foreign oil.
||Biodiesel - Biodiesel comes from renewable plant sources, such as oils from vegetables, peanuts, soy beans, canola/rape seeds, hemp seeds and some grains which are domestically and abundantly available. More specifically though, biodiesel refers to plant-derived diesel that has been subjected to the process of transesterification, a chemical modification of ordinary vegetable oil which makes the fuel meet high industry standards (ASTM D6751) for usage in diesel engines [see notes below] and prevents it from solidifying at colder temperatures. Sometimes biodiesel is mixed with petroleum diesel in different proportions and still sold under the name "biodiesel," even though the biodiesel content may be as low as only 5%. Biodiesel and petroleum diesel mix extremely well and commercially available blends use the labelling B5, B20, B50 or B100, to reflect the percentage of biodiesel to regular diesel. Biodiesel in pure form produces significantly less emissions than petroleum diesel and zero sulfur emissions.
||Straight Vegetable Oil (SVO) - Straight vegetable oil refers to any vegetable oil that can power diesel engines but has not been optimized (through transesterification) for usage in automobile fuel systems under all temperature conditions. The major drawback of using SVO is that it gels at colder temperatures and must be heated prior to reaching the engine's fuel injectors during cold weather. You can buy cooking oil and use it straight from the bottle (very expensive), or you can get it used from restaurants, which is commonly called Waste Vegetable Oil (WVO) [photo]. WVO must be filtered prior to use since it contains many food particles. SVO/WVO are derived from plants such as peanuts, soy, canola/rape seed, and other grains. Both thicken at colder temperatures and can clog fuel systems unless they are heated and filtered before reaching the engine (vegetable oil can even solidify below 25 degrees Fahrenheit). Vegetable oil conversion kits include a heating system and usually a second gas tank [photo] to circumvent the cold weather issues. SVO also produces extremely low emissions.
Pros and Cons of Converting a Diesel Engine to Run Vegetable Oil
"Biodiesel is the only alternative fuel to have fully completed the health effects testing requirements of the Clean Air Act. The use of biodiesel in a conventional diesel engine results in substantial reduction of unburned hydrocarbons, carbon monoxide, and particulate matter compared to emissions from diesel fuel. In addition, the exhaust emissions of sulfur oxides and sulfates (major components of acid rain) from biodiesel are essentially eliminated compared to diesel."
Lyle Pearl's article on biodiesel (PDF 56KB)
|Lyle Pearl of Santa Fe, NM and his wife Tatiana pose beside their 1980 Mercedes that they recently converted to run off of used cooking oil.
|"This is technology that is here now, not a technology of the future like hydrogen.."
- Lyle Pearl
- Diesel engines are uniquely suited to run vegetable oils because the inventor, Rudolph Diesel (1858-1913) originally designed them to run off of peanut oil. Even though the first diesel engine was patented (No. 67207) in 1892, today's diesel engines are not much different from Diesel's first engine. Thus, they are ready, willing and able to run on all kinds of environmentally friendly fuels.
- Saves money on fuel costs.
- Reduces emissions. There is a 90% reduction in emissions when choosing to use pure biodiesel over petroleum diesel [see references below]. As oil-bearing plants such as soybeans grow, they take in carbon dioxide (CO2) from the atmosphere. The same amount of CO2 is released back into the atmosphere when vegetable oil is burned. This process is referred to as being “Carbon Neutral” because there is an equal exchange in carbon dioxide uptake and release. Burning fossil fuels continually adds to the carbon load of the atmosphere. The current planetary carbon dioxide output is well beyond the Earth’s natural ability to trap it and the atmosphere has the highest CO2 concentration in modern times. Most scientists believe this to be the cause of global warming.
- Recycles waste oil from restaurants.
- SVO can (and is) made domestically using renewable crops, employing farmers and helping the local economy.
- Make a positive political statement. Decrease your reliance on a system that you may criticize. There are alternative sources of energy, now! Help create a new system, one that reflects your values.
- Biodiesel exhaust smells like popcorn!
- Some vehicle warranties can be voided by installing a conversion kit and/or using biodiesel. If you have a relatively new car that's still under warranty, this is an important concern and you should check with your car manufacturer.
- Gathering used oil is messy work. But as the alternative fuel movement gains in momentum, fuel and supplies are becoming more available and easier to implement.
- There is mixed data on how SVO affects engine life span. Some say the life span is reduced: "McCormick, a senior fuels engineer for the National Renewable Energy Laboratory in Golden, CO, said studies have shown that running vehicles on vegetable oil can reduce a car's lifespan. 'Those vehicles aren't going to last as long as they would running on conventional fuel,' McCormick said. 'Diesel engines are supposed to be low-maintenance and long-lasting engines. Running on straight vegetable oil, I don't think that's going to happen.'" Source: The Kansas City Star; "One Man's Fish Fry Grease is Another Man's Vehicle Fuel" March 29, 2005. However, many others claim the opposite; "engine wear is greatly reduced, sometimes tripling engine life for engines running on straight vegetable oil." Source: www.distributiondrive.com.
Case Study: Converting a Stock 1980 Mercedes Benz 240 TD Diesel
So now that you know a little about the pros and cons of converting your diesel engine to run on vegetable oil, let's look at the steps it takes to do the conversion:
Step #1: Find a diesel vehicle
Our co-author Lyle Pearl, of Santa Fe, NM purchased a 1980 Mercedes 240 TD in good running condition with 143,000 miles for $2,700. Any modern diesel engine can be converted as long as there are no rubber seals used in the fuel system (only older diesels use rubber seals). Since vegetable oil is a strong solvent, the rubber seals can deteriorate and fail.
Step #2: Buy a conversion kit and self-install or have it installed by a mechanic [see links to suppliers below]
Lyle bought a two fuel tank conversion kit for $500 and found a local mechanic familiar with conversions who installed it for $1,000. The car's original tank was kept and holds regular diesel (or B20, B100) fuel for cold weather starting. A second tank was installed in the trunk for vegetable oil. Hoses are run from the car's radiator to the tank to heat the oil via a heat exchanger before it enters the final fuel filter and injectors inside the engine compartment. Here are some photos of the whole setup (Click on photos to enlarge):
|Easily-installable Vegetable Oil Conversion Kit purchased for $500 from Greasecar.com (photo shows VW Golf kit).
||A second vegetable oil tank is installed in the trunk. Fuel line and warmer hoses can be seen in the top right. Overflow line is on the left.
||Two hoses cycle hot water from the radiator to heat the vegetable oil before it reaches the engine. The fuel line is also wrapped with these hoses and can be seen exiting the upper right of the tank.
|Here you can see the hose splitter which sends hot water from the radiator to the veggie tank in the trunk. The veggie oil must be hot before it reaches the engine to prevent solidifying.
Step #3: Get the Vegetable Oil
Vegetable oil can be made from soybeans, sunflower seed, rape seed, corn, palm, hemp seed and even algae. The easiest source is to by new vegetable oil, but it's not economical right now since the price is higher than diesel. The most economical and recycle-conscious source is to collect it for free from restaurants, specifically Chinese or Japanese, due to their cooking methods. A superior oil will be amber in color and is referred to as “liquid gold.” Oil from other types of restaurants may also be suitable but may require more filtering to remove food particulates.
Now you are in business! The car starts up on regular diesel fuel, B20, B100, etc. from its normal gas tank. Once the vegetable oil is warm (<15 minutes depending on weather), a switch in the cabin [photo] is manually thrown allowing pure vegetable oil to flow and take over as the fuel source. The switch is thrown again a few minutes before stopping for a prolonged period of time (roughly 10 minutes depending on the temperature) to make sure the vegetable oil is purged from the fuel line and injectors so that they don't become clogged when the engine is started cold.
In warm weather climates the car can be started and run completely on vegetable oil, but it's a good idea to have the regular diesel tank since you may run out of vegetable oil or want to travel to a colder climates. Also, follow the weather since the air temperature may cool down quickly after the passage of a cold front. Purging the fuel line and fuel pump/injector with B20 or regular diesel will insure that you are not caught by surprise should the weather become cold.
That's it! Once the conversion is done and you've secured a source for your free veggie oil, you're on the way to kicking the petroleum monkey off your back, lowering emissions, saving radically in fuel costs, and having the satisfaction self-determination vis-a-vis the oil problem. The biodiesel revolution is REAL and happening now all over the world. It's big and it's growing fast! Join the thousands of progressive individuals who have made the commitment to doing something about a problem rather than just complaining about it. Read more user experiences with vegetable oil conversions on Greasecar.com's User Profiles section and find out even more by exploring the links below.
Doug Watson of Ohio conducted a horsepower (HP) Dyno performance test on his 1995 6.5 Ltr. Chevy. The results from the test performed on October 21, 2004 are 151.7 HP while running on vegetable oil, compared to 145.3 HP on diesel. This is encouraging, but not conclusive being only one study. Anecdotally SVO seems to offer as good or better performance.
Mr. Watson also conducted a standard opacity emissions test on his 1995 6.5 LTR Chevy at a State of Ohio official vehicle inspection station. The vehicle released 3.4 ppm (parts per million) when run on diesel fuel compared to 1.8 ppm when run on vegetable oil. Burning diesel fuel released almost two times as much visible pollution as vegetable oil does. There is no sulfur in vegetable oil and therefore no sulfur in the emissions! There are sulfur dioxide emissions from the burning of petroleum diesel since low-sulfer diesel is not widely used in the USA . Sulfur dioxide emission lead to acid rain and other problems. Burning biofuel is still a logical choice over diesel as biofuel releases 90% less toxic chemicals. Carbon monoxide is reduced by 40-60% and overall carcinogens are reduced by 90% Hydrocarbon emissions are reduced by 50% which reduces photochemical smog (ozone) by 50% as well. Particulate matter, a major contributor to increased asthma cases, is reduced by 45% (see: Veggiebus.com's FAQ.) This is similar to the findings from the emissions study conducted by Doug Watson on his 1995 Chevy.
The process of making biodiesel from SVO/WVO is not complicated. It is done through a simple chemical process known as transesterification (similar to saponification--the chemical reaction used to make soap out of a vegetable oil/animal fat.) Vegetable oil is collected then heated to between 120-130 degrees Fahrenheit, and then filtered to remove any large particles such as french fries or tempura. Methanol (20% of volume) and sodium hydroxide (lye at 3.5-9 grams per liter) are mixed, then added to heated vegetable oil, then mixed again for one hour. The mixture is left overnight and the glycerin by-product settles to the bottom of the container. The top layer is a vegetable based fuel ready for use ( source: greaseworks.org.)
PDF document detailing transesterification process (36K)
Rubber engine seals in older vehicles must be replaced since biofuel has strong solvent properties. All newer diesel vehicles are fit for B100 since there do not use rubber seals. This page has more info about the rubber seal issue.
It may be beneficial to use a fuel injector/piston cleaner every six months to remove any accumulated carbon deposits. Simply pour the 12 ounce bottle into the tank and drive off.
A story did emerge in the 1990’s that told of possible coking of vegetable oil (carbon build up on the pistons and fuel injectors) from the incomplete burning of the fuel. This seems possible in theory and simple back-up systems provide safeguards.
Resources On The Web
Lyle Pearl's original essay that inspired this article (PDF 56K)
Getting Started with Biodiesel - from the Berkeley Biodiesel Collective. Cars for sale, supplies, discussion forums, etc.
Biodiesel.org - the national trade association representing the biodiesel industry as the coordinating body for research and development in the US.
Bio Diesel Academic Research Hub - University of Missouri-Columbia
The Clean Fuels Development Coalition (CFDC) - 20 year old nonprofit.
Ecoversity - Santa Fe, NM based school offering biodiesel workshops.
Biodiesel of America - Non-profit site that grew out of Josh Tickell's Veggie Van Organization and is working to convert school buses. Info, forums, products.
"Fields of Fuel" - Documentary on biodiesel
American Biomass Association
VW Golf TDI Biodiesel information - owner review of Golf TDI with biodiesel info
2008/2009 VW Jetta TDI Bluetec - Latest clean diesel technology from Germany makes VW Jetta clean in 50 states.
2008 Mercedes Benz E320 Bluetec - Latest clean diesel technology from Germany makes Mercedes Benz E320 clean in 50 states.
Biodiesel Facts vs Myths
Goodgrease.com - Biodiesel activist site with excellent forums
LocalB100.com - Biodiesel, biodiesel homebrewers, and small-scale commercial producers
JourneytoForever.org - How to make your own biodiesel
BiodieselTutorialWiki - Collaborative Biodiesel Tutorial Project's development wiki
Collaborative Biodiesel Tutorial Workgroup - Active biodiesel forum
BiodieselBlog.com - Run by Eric Case of Google
More Biodiesel Blogs
WVOfuels.com - Website dedicated to waste vegetable oil fuels
Calcars.org - California Initiative for Plug-in Hybrid Vehicles. They're not promoting biodiesel, but they're doing great things with hybrid electric vehicles, modifying cars like the Toyota Prius to get over 100 MPG.
BioBronc.com -Project to convert a Ford Bronco to run on biodiesel. Also an interview with project creator Megan MacMurray.
Companies Offering Biodiesel Products and Conversion Kits
Conversion kit and filters in this article: Greasel Inc. - popular small US company selling conversion kits and supplies
Conversion Kit Reviews - from Fusel.com
Frybyrd - conversion kits and fuel.
ELSBETT - single tank system from Germany
Grease Car.com - SVO fuel systems, classifieds, discussion forums
Neoteric Biofuels Inc - Berkeley, CA Single tank kit conversion kit company
Oil Press.com - Swedish company making converters
Vegburner - UK consulting site on SVO with performance reports and test, papers, links and services
Goat Diesel Inc - database of vehicles that can be converted to run vegetable oil
Biofuel Oasis - worker owned company in Berkeley, CA that sells high quality commercial biodiesel
Blue Sun Biodiesel - Biodiesel production and processing company based in Colorado
Singer Willie Nelson's "Bio Willie" - diesel fuel, supplies, and info, "Family farmers growing fuel for America and the world"
"The Vegetable-Oil Alternative" - Car and Driver Magazine, 2005.
"One Man's Fish Fry Grease is Another Man's Vehicle Fuel." - Motortrend Online reprint of a Kansas City Star article, 2005.
"SVO Speedwagon: On hybrids vs. veggie-oil cars" - Grist magazine, 2005.
"Green and Comfy" - New York Times, 2004.
"Veggie Fuels Feed Bottom Line" - Wired.com, 2003.
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