At the suggestion of Terrainer I thought I would post some information about my experience as well as some general information that would be of interest to others who might be thinking of doing the same thing. Around 2005 while I was still in college, I heard that diesel engines could run on vegetable oils, so I started searching on the internet. One of the first places I found that was a wealth of information was this:
http://biodiesel.infopop.cc/6/ubb.x?a=cfrm&s=447609751
Most of you have probably heard of biodiesel, the manufacture and use of which is discussed on the abovementioned forum, but I actually don't use biodiesel-my vehicle has been modified to be able to burn straight vegetable oil, commonly referred to as SVO. Biodiesel is vegetable oil that has been undergone a chemical change in order to remove the glycerin in the oil which makes it less viscous. Viscosity of the fuel in a diesel engine is extremely important. Fuel that is too viscous will not properly atomize and ignite, which ultimately will foul the injector and cause deposits in the cylinder itself. Straight vegetable oil is too viscous to be used as fuel at room temperature, so you have two choices-either change the fuel by chemically making it less viscous (making biodiesel), or by doing something a bit more simple-heating it to at least 160 degrees. Biodiesel does have it's advantages, because it is essentially just like diesel fuel-it can be used in any diesel vehicle without any modification to the vehicle, but it requires the use of chemicals (lye and methanol) that must be purchased, and it the process of producing it can be complicated. That being said, a visit to the abovementioned forum will tell you everything you need to know about making biodiesel.
As I said before I have converted my truck so that it can burn SVO. Basically this consists of a secondary fuel system with a separate tank, filter, and pump that stores and feeds the oil to the truck when needed. The system also contains a heat exchanger which uses heat from the truck's cooling system to bring the oil up to 160 degrees prior to it reaching the injectors. At 160 degrees the oil has a the same viscosity as diesel fuel and will atomize and burn properly. This is extremely important, because even if the oil is properly filtered and is free of water, if cold oil is injected into the cylinder it can still cause damage. This is why a two tank system is critical to using SVO as fuel. The complexity and sophistication of systems vary, but I'll just detail how mine works since that's what I'm most familiar with:
Starting: The truck starts on diesel fuel as it normally would, as diesel fuel is suitable for starting at any temperature. As the truck warms up, two sensors monitor the temperature of the oil in the secondary tank and the engine temperature.
Switching to vegetable oil: Once both pre-set temperatures are reached, the SVO pump activates, drawing oil from the secondary oil tank through the heat exchanger, and into each bank of cylinders. At this point the stock diesel pump shuts off as it is no longer needed.
Running on vegetable oil: The system continues to monitor for proper temperatures and SVO fuel pressure. If SVO fuel pressure drops (ie: you take a hard turn and the fuel pickup is starved or you run out of fuel) the diesel pump kicks in-once SVO pressure is restored it turns off again. The transition takes a fraction of a second and is completely seamless.
Shutting down: Running on SVO has one caveat-the lines must be completely purged of SVO when the truck is shut off, because leaving SVO in the lines to cool would cause problems starting later, and ultimately engine damage. The system I use takes care of this by using a timer which begins when the truck is turned off via the key. After turning the key to the "off" position and removing it the truck starts a purge cycle-the SVO pump shuts off and the diesel pump fills the lines with diesel fuel, ensuring a problem free start later on.
The company that manufactures my system used to be called Dino Fuel Alternatives, but they were bought out by another company called BioFuels Technologies-they still manufacture systems for the 7.3L and 6.0L Powerstroke diesels. I believe they have also started manufacturing a "generic" system that can be adapted to other uses as well. Check out their website here:
http://www.biofuelstechnologies.com/
In addition to BioFuels Technologies (who mainly concentrate on Powerstrokes) there are other companies out there, but doing your homework and paying attention to quality is important. There are also a lot of inferior kit makers out there looking to make a quick buck-there were TONS of them on the market when diesel hit $5.00 a gallon two years ago. Also, the Infopop Biodiesel and SVO forums are a wealth information on everything from DIY conversions of all types of vehicles, sourcing, collecting, and filtering free waste oil from restaurants, and lots of other topics. That should answer a lot of the questions about this subject, but I'm happy to answer any others that come up.
