I converted my F250 to run on waste vegetable oil about a six weeks ago. I've got a 100 gallon tank in the bed dedicated for waste vegetable oil. The tank is heated with engine coolant diverted through several heater cores at the base of the tank. I also have a heat exchanger under the hood to boost the vegoil temp as little more before injection. My vegoil is being injected at approximately 150 Degrees F, which is almost perfect, as that is the temp at which the viscosity of the vegoil approaches the viscosity of diesel.

A six port valve with a switch on the dash controls which fuel is being drawn into the fuel pump. You have to remember to shut down on diesel to prevent the possible coking of vegoil in the injectors of Direct Injection diesels after shutdown (coking in the injectors is a theory. Not sure if it is proven or disproven yet) Starting up on diesel is also much easier when the weather is cold. Once you take off and the engine comes up to temp you can flip the switch and start burning the vegoil again.

I've got just under 3000 miles on so far with no problems. Power and mileage remain unchanged. One benefit (other then free fuel and lesser environmental impact) is that acceleration is significantly quiter when burning vegoil. I assume it's because combustion is a tiny bit slower. I'll have another 1000+ miles by the end of next week.

The following a some links I used for some excellent info. Their conversion kits are a bit pricey. I made my own.

http://www.greasel.com/body_index.html
http://www.vegburner.co.uk/votheory.htm
http://danalinscott.netfirms.com/thebasic.htm
http://www.greasecar.com/products.cfm?productID=1

Good Luck