Using Vegetable Oil as a fuel: (from the greaseworks website)

Modern day diesel injection systems, having been engineered for thin, low-viscosity diesel fuel, cannot handle high viscosity vegetable oils--unless, however, the viscosity is reduced. This can be accomplished two ways: chemically (transesterifying the oil into biodiesel); or thermally. By heating the oil to 160-180 F the viscosity is reduced to that of diesel fuel and, voila!, Sir Rudolf Diesel has his dream revisited.

Leaning on the ethos of Permaculture ("nothing in the system goes to waste"), heating vegetable oil in a vehicle is accomplished by tapping into the coolant system and employing a simple heat exchanger in an auxiliary SVO dedicated tank. Alternatively, 12-volt electric heaters may be used to heat the tank, as well as inline, to heat the oil before it reaches the injection pump.

This is an oversimplified rendition, but the principle is solid: Heat the oil with waste heat from the engine (or electricity) and you've got yourself a renewable, sustainable alternative-fuel.

Real World:
There are 2 types of systems. Single tank and 2 tank systems. For the most part Mercedes Benz diesels form the 80's & early 90's will work as a single tank system. That is to say that instead of diesel fuel you use Vegetable Oil. In this situation you could also run various "blends" of say 50/50 - 50% vegetable oil & 50% diesel/biodiesel. Somepeople vary their blend based on the season. I did not investigate these vehicles so I do not know much about these conversions. Search the forums for more info.

The other option and the one that applies to most applications is the 2 tank system, both diesel & vegetable oil tanks are utilized. The vehicle is started on diesel until it is at it's operating temperature. As the engine is approaching operating temp the engine heat is being used to heat the vegetable oil and reduce it's viscosity. Once the appropriate engine temperature is reached, generally around 190F, the car switches to VO. This is either accomplished manually or automatically depending on the conversion kit chosen. There is no noticable change in the cars operation when swicthing over and thereafter.

Different kits achieve the temperature goals in different ways. Engine heat is always used but some kits (such as Fattywagon & Plantdrive) use electricity as the final heating stage. Once on VO you drive until you need to shut down the vehicle. When it's time to shut down the vehicle you "purge" the VO from the system. Purging replaces the VO in the engine with diesel so that the car can restartwhen cold. Remember the VO is thicker then diesel and is a problem for a car to restart on (except the Mercedes Benz's mentioned above). Purge times depend on the kit choosen.

Now, what happens when you just want to get a cup of coffee and are away from the car for 5-10 minutes? There are different opinions on this. Some people say to always purge no matter how short the time car is off. Plantdrive, the maker of my kit says, depending on the outside temp, that it's OK not to purge if away for no more then 30 minutes. On the otherhand, Frybrid claims purge times of less then 10 seconds (3-5 on VW's!). In that situation is it very easy to purge?

Currently most of my driving is short term and there is a learning curve involved in when to purge or not. Unless you have a kit that can purge very quickly - a few seconds or you are willing not to purge while turning off the car for short periods VO is not going to work. It's just not practical to spend a minute or 2 prurging everytime the car is turned off when for short periods. The greater the distance you drive between starts and stos the diesel you use and the more practical the VO conversion is.

There are also concerns on where the purged VO is sent. This is the dreaded "looped" return issue. I'm not going to go into this now other then to say some folks say you should loop the return & others say you shouldn't. Again search the forums

If you decide to collect your own used oil it is best to