I did hear that if you buy a pallet in sainsbury's, It works out at 36p a litre. You have to ask for the manager.
My mate bought a pallet to run his pajero.
Not been in myself but worth researching at that price.
lots of people do but from what ive read you need a good source as meat can congeal(hope thats spelt right) in the oil and block ya pipes,like if you fry sausages in a pan. it will also collect water/moisture and need heating to rid it of this(that poppin noise when the fryer is switched on is water being boiled in the oil). just what ive read but it can save a fortune in the long run, never tried myself, no space!