Avoiding Engine Trouble When Running Vegetable Oil in your Diesel

Fuel injectors will need the most attention

Like everyone else involved in running SVO / WVO, I love driving on free fuel. This was especially intoxicating when diesel fuel prices were approaching $5.00 a gallon. But contrary to what you may hear on some forums there is no free lunch. There is a maintenance price to pay. In fact, there are a few common myths surrounding this subject which I really think need to be brought into the light. Chief among them is the belief that if you can just get the temperature of the oil hot enough before it is injected into the combustion chamber - then all is well - and you will have no problems.... The trouble is no matter how hot you get the oil you can not expect all the glycerin in the oil to burn in the combustion chamber. When it doesn't completely burn it leaves a very hard crust on the injector tips and in the pre-chambers. When it comes to combustion, the health of the engine and the condition of the fuel injector tips are even more important than the temperature of the injected oil.

Problem & Solution

Common among these chassis:


If the diesel engine does not have strong compression you will not get complete combustion of the oil fuel. If the injectors are not spraying properly, excess oil will be left in the pre-chamber  and combustion chamber to form coke like you see here on these injectors.  And it keeps going down hill from there!  It is a vicious cycle. Poor spray pattern leads to more injector tip coking and that leads to even worse spray patten which causes the tips to leak and then even more coke is formed.  Take a look at how badly that injector is spraying - it is supposed to be a mist not a squirt!

The best improvement you can do if you are running SVO is to install our high performance Monark fuel injector nozzles. They spray with a finer mist pattern than Bosch and are ideal for alternative fuels. The other thing I highly recommend you do is remove and clean the injector tips and ream out your glow plug holes every 12,000 (lots of short trips) to 24,000 (heavy freeway driving) miles if you are running straight vegetable oil.