yeah it's got cooking oil as its base. the cummins forum i'm on has a thread going about this right now too. 1 guy says he uses it pretty regular but the other 10 or so said to stay away from it. but they didn't have any actual experience with it. i have a funny feeling it one of those too good to be true things.
The main problem with that system is that you have to be able to collect all that used fryer oil. Then that oil still has to be filtered, dewatered and stored. By the time this is all said and done you have a lot of time invested. Now I don't know about ya'll but I have better things to do with my time than go around begging for used waste oil. Besides, once these resturant owner's realize they can sell this stuff the cost advantage will disappear.