Tuesday, October 16, 2007

The Bad news

Oct 11th 2007
I came across this post while googling "WVO TDI Jetta". I can not stress enough that one should weigh the advantages and disadvantages to using SVO in a modern diesel. Here is a followup thread from Greasecar.com

I had previously spoken with the owner of the above mentioned car, I was referred to him by Plantdrive since he also had a Jetta TDI and their TDI kit. He had been running his for about 2 years before I installed mine and was located in Atlanta. I spoke to him over the phone because I just wanted a users feedback and he I had a couple questions. 2 things come to mind when I compare my situation with his and the gentleman running the 2005 Passat who has had similar problems and a stock Plantdrive kit.

In both situations I believe they switched over to vegetable oil to soon, not giving the engine time to get hot enough. The Passat owner mentions in his earlier blog postings that he would switch over a few minutes after starting the engine. The other gentleman mentioned when I spoke with him that he switched over as soon as the water temp gauge started moving, as this indicated that the thermostat had opened up for flow to the heater core. IMHO, this does not mean that the engine is at operating temperature. I am also running additional heaters on my car.

There are 2 problems that I am aware of with vegetable oil, one is viscosity and the other is proper burning of the oil in the combustion chamber - the atomization of the fuel if you will. If the fuel doesn't burn right - and it's arguable that it ever does - the excess oil cokes (gunks up) the piston rings allowing engine oil to mix with crankcase oil and it destroys the lubricancy of the motor oil. This leads to scoring of the piston wall, the gunking of the valves and damage to other parts of the engine due to friction.

Second, if the veggie oil is heated it reduces viscosity, reducing strain on the IP and providing a better spray pattern for the injectors. A hot engine will burn the oil fully by helping to vaporize the oil in the chamber. Frybrid has a good analogy on their site along with other great resources -

"Imagine placing a pan on the stove, pouring a small amount of vegetable oil in the pan, and turning the heat to high. The pan will begin to heat up and as it does it will heat the oil, around 300F the oil will start to smoke, then turn black, stick to the pan. . . . . (get a new pan and) turn the heat on high again. When the pan gets to about 600F throw a tablespoon of oil in the pan, just before it bursts into flame singeing whatever is left of your eyebrows, you will notice that the oil is skittering around the pan on a layer of vapor, none of the oil is sticking to the pan and none of it is turning to carbon.

This is what happens in your engine.

Anther thing I remember about my conversation with the gentleman in Atlanta was he told me that he would drive to work and not purge, leaving the car for several hours before restarting it on oil. This is a major error never do anything along those lines. Sure I don't purge for 20 minutes pit stops if it's a summer day, but anything longer or colder then that I purge.

The other thing both drivers did not do is dewater the their oil. I'm not really sure of what water does exactly other then I heard that is will damage the IP and pit the combustion chamber. As with everything else I say - take it with a grain of salt and make your own conclusions

I purchased a car with 126,ooo miles on it and I'm willing to see how far I get. I happen to change my oil roughly every 3ooo miles just because I don't drive that much and I always did it with my gasoline vehicles. I use soy oil which is the worst offender for contaminating the engine oil because of it's chemical make up but it is the most readily available.

- Pick a high mileage car & a car out of warranty
- Make sure the engine is hot before switching over and the oil is as hot as is practically possible
- purge the oil back to the oil tank and don't mix it with the diesel tank - especially if the tank is small
- Dewater and filter your oil down to at least 5 microns
- Change oil in 1000 to 3000 mile increments

Realize that:
- Over a period of time you may be damaging the engine
- Driving longer distances is better as the engine is hot and it will burn the oil better
- You are a beta tester and may be ruining your car in the process.