the set up consists of two tanks, one with a heater (running coolant from the engine) for the oil, and your regular disel tank. there is also a seprate fuel line with a filter for the oil, and a selenoid to switch back and fourth. whale living with the roomate who had the setup some problumes were evedent, its definatly not for everyone. the first thing is that it is really messy, if you have the tank in your trunk, its going to smell RANCID! if you go for a more proffesional install and mount it somwhere under the vhicle you wont have this problume, but it will also be hard to access the tank if you need to, and good luck finding a spot under there if your running an old VW. collecting can be a pain, certin sources not having adiquite quality oil. the main drag is filtering, not only do you have to have a heated space (witch will also smell RANCID) but you eather have to spend a butload on filter bags or have enough space for a couple 55 gallon barrels to sit and settle for a couple months.
you can check more info at www.greasel.com, but I wouldent recomend buying one of there kits. the one my freind had was full of second rate non automotive quality materels (hardware hoses and clamps,etc), a plastic tank that they just cut a hole into and calked and screwed a plate with the heater into, and other junk you could just buy or do yourself. I could have made him a much higher quality systm for the same price.