Can a Diesel Engine Really Run on Vegetable Oil?
By Erick Panger
LESK WVO Conversion
Well if you consider that Rudolph Diesel the inventor ran his first engine on vegetable oil then the answer is obvious, yes it can. But with today's modern engines and higher pressure fuel delivery systems, there are some steps to take before you just dump the oil in and go.
Most conversion are of the two tank design. This is not to say you could not run a one tank system, many do, but the two tank design seems to works best for most diesel engines. A simple two tank system can give the flexibility of starting and stopping on diesel and running veggie oil in between.
The basic steps to getting into and using veggie fuels successfully are, have a diesel vehicle, have a source for waste veggie oil (WVO), prepare the WVO, and modify the vehicle.
Having a vehicle is key, having a diesel vehicle is even more important. Each time I describe my truck and how I use WVO on a daily basis most ask, can I do this with my car. I always ask is it diesel? They say no and I say sorry only works with compression ignition engines. The brand and type of vehicle is almost limitless, as long as it's diesel. There are a few known exceptions. Some vehicles built with certain injector pumps do not do well on WVO. Then, other vehicles do so well that they still sell for a premium 25-30 years after they first rolled off the assembly line. (See reference for more detail)
So you have a vehicle and now want to run WVO. Well think about how many restaurants there are in your neighborhood. They are all potential fuel sources. See most restaurants change their fryer oil weekly, some more often some less. All have to follow local rules for disposal. They normally have to contract with a rendering company. That company will deliver a grease dumpster and often charge a few to empty it. There are a few places were the oil is becoming more valued and the restaurants get five or ten cents a pound for the waste. In any case you can ask the owner for the oil. If they are willing to place it in your container, or better yet back in the plastic 4.5 gallon cube it comes in, you're all set. Never take oil from a grease dumpster, that would be stealing. The owner likely does not even have permission to grant you access to the oil once it's in the grease dumpster. The best types of restaurants are the small mom and pop places. Larger chains often will not even want to talk to you.
Ok you have oil. You lined up two or three sources and now you have this stuff sitting around in cubes. The next step is to prepare the oil for use. Looking at the oil in a cube is the best way to see what you have. I get some oil and it's perfect, slightly darker from the frying but other then that no crumbs, food stuff, or visible water. I get others and you have a clear line of demarcation water, sludge, food crumbs floating, and then some oil on top. All of this I treat the same let it alone. Leave it sit in a warm place, say 60 degrees or more. The more time you let it sit the better you are. I often let my cubes sit for two weeks, others let them sit even longer. The next step is to filter it. There are plenty of opinions on how to do this. I pour mine through a 5 micron sock filter. It ends up in a 55 gallon drum. There it is heated to around 90 f for a few days. After that I run it through two inline filters on its way to my storage drum. The amount of time it takes me to accomplish this is only about an hour a week of. So it is not a huge effort once you have things setup. One last thing to do before you are ready to burn this as fuel is to test for water. (See reference for link to water tests)
Now you have clean dry WVO what are the best ways to use it. Most agree that you need to add a second fuel tank, fuel filter, and a heat source or two, and a way to switch between the two fuel tanks. Many add second fuel pumps as well. The heat is required to get the WVO to about the same viscosity as #2 Diesel, most agree that's 160F. The coolant system is one of the best ways to do this. But adding electric heaters to the system is also common. Most use the coolant to heat he fuel in the tank and well as, as the WVO travels in the lines towards the motor. You can often also find some sort of electric heat just prior to the IP or before a small filter and then the IP. You'll end up with a switch or two in the cabin of the vehicle to make the switch between the two fuels.
Well these are the high level steps to use waste veggie oil in a modern diesel engine. This article is in know way the exact process and anyone considering using WVO to fuel their vehicle should do further research. There are many internet forums on the subject some specific to vehicles and other not. For Ford specific talk FTE is IMO by far the best Ford truck forum.