Rudolf Diesel invented the diesel engine in the late 1800's. When he exhibited his engine at the Paris World’s fair, it was with peanut oil as the fuel. He envisioned his engine as being able to run on multiple fuels, including vegetable oil.
"The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become in course of time as important as petroleum and the coal tar products of the present time," - Rudolf Diesel, 1911
We can always hope, but the facts are that if we used all our farmland to grow vegetable oils, we would only be able to replace a small percentage of petroleum diesel fuel.
In the beginning, the diesel engine would run on just about anything with enough BTUs. Over the years, it was fine tuned to run more efficiently on petroleum. In order to improve reliability and reduce emissions, the fuel has been changed. All of this “improving” prevents us from dumping vegetable oil directly in the fuel tank of modern diesel engines.
SVO or Straight Vegetable Oil will, in most cases, work fine in diesel engines for a tank or two, but for long term use, we need to make some changes or reliability suffers. There are three options:
- We can chemically alter vegetable oil to give it properties more resembling diesel fuel. (aka make biodiesel)
- We can blend our vegetable oil with solvents like gasoline and turpentine to give it properties closer to diesel fuel.
- We can modify our diesel engine so that it can operate reliably longer on unmodified vegetable oil.
Making biodiesel requires purchasing and working with dangerous chemicals. Making biodiesel also generates a hazardous waste stream that causes all sorts of problems. There has been a lot of research on making, and using biodiesel, and we know it can be used indefinitely while maintaining a high degree of reliability.
Blending modifies the fuel without most of the problems of making biodiesel, and you don’t need to modify your engine. It is highly experimental and while some have run over 50K miles with no problems, others have had to replace the entire fuel system after only a few thousand miles. Blending is best done on an older (disposable) vehicle.
Converting your vehicle to run reliably on vegetable oil can be a little bit expensive. Once converted, the cost is less than 50 cents a gallon. That is if we use WVO (used or Waste Vegetable Oil) that we collect from kitchen fryers. New, unused Vegetable oil can cost significantly more.
Vegetable oil will absolutely burn in diesel engines. Study after study finds no short term effects from adding up to 50% vegetable oil to diesel fuel. The long term studies however indicate engine life is shortened due mostly to carbon buildup in the engine.
Modern diesel engines are fitted with injection systems designed to deliver and properly atomized diesel fuel with a viscosity of approximately 8 centistokes. Common vegetable oils are 10-20 times more viscous (thick) and cannot properly atomize in stock systems. Thicker more viscous fuels have larger droplets out of the injectors than fuels with the correct viscosity. These larger droplets do not burn completely. Indirect injection (IDI) engines have a little pre-combustion chamber where the fuel gets sprayed first, before the fireball expands into the cylinder. Big droplets of fuel just splatter against the very hot walls of the pre-combustion chamber, vaporize and eventually burn completely. DI (direct injection) engines run the risk of accumulating partially-burnt fuel on the cylinder walls. If the fuel droplets are too big to finish burning before hitting the cylinder walls, the oil sticks to the cylinder wall because the cylinder walls are not hot enough to vaporize it like is done in the pre-combustion chamber. The rings scrape off this partially-burnt goo, which bakes itself into the ring grooves, gluing the rings in place. This is called “piston ring coking”. The result of piston ring coking is a loss of compression and cylinder wall scoring if left uncorrected. The only way to repair the damages is to tear down and re-ring the engine.
If coking is not resolved as soon as it is identified, fuel can blow by the seized rings diluting the crankcase oil with fuel. Once in the crankcase, vegetable oil will polymerize making the lubricating oil thicker and ineffective as lubricating oil. The result is catastrophic engine failure. Loss of lubrication has been known to cause loud knocking noises and sometimes will cause the appearance of large holes in the engine block.
Picking the best cars and trucks for SVO conversions is a difficult task. It can't be done without expressing an opinion. I've polled various SVO experts and conversion kit installers and here are the results. Be sure that those polled did not all agree with the list. It was common for them to add or subtract a vehicle from the list. So far the challenges to the list have been divergent in both the adds and the subtracts with no two experts making the same changes. The common theme was the adition of a newer model to the list and a complete confidence in their ability to convert any diesel to SVO.
article submitted by Greasecar.com
General Deisel Maintenance
Changing fluids and filters
Though Diesel engines do not require regular tune ups like gasoline engines, they still require maintenance to optimize and maintain engine health. The most important things to service are filters and fluids. Your vehicles owners or service manual will lay out filter changing intervals. A dirty fuel or air filter can seriously hinder power and fuel economy. Lubrication oil should be changed regularly with oil specified for diesel vehicles and the coolant system should be flushed every year. There are also a number of diesel fuel additives that can be used to minimize injector tip fouling and fuel gelling.