thats bullshit red derv is only for use for agricultual vehicles such as tractors and plant machinery, its untaxed and actually against the law to use it on the road vehicle unless its been approved, chip fat isnt against the law to use it just states that you must keep a record of it and tell the tax man at the end of the year, soo unless you have no common sense you cant get done, and as to thinking about actually paying the tax man WHY u might as well spend 1pound a litre on white!