Used frying oils/fats (UFO) can be applicable as fuels for standard diesel engines directly after treatment or after their chemical modification. UFO represent a perspective cheap and available source of natural triacylglycerols with considerable potential. Project consisted of scientific activities in two directions: 1. treatment of UFO to the quality of DIN 51 605 for direct combustion in diesel engine with adjusted fuel system, 2. catalytic cracking of UFO with the aim to obtain liquid product exhibiting similar characteristics to fossil diesel fuel at maximal yield after treatment. Increased acid value was solved. Horizontal vacuum evaporator with wiped film has been utilisable as reactor with wiped film for UFO cracking.