I am not sure it would be illegal if you were to pay HMRC the required duties (as diesel owners running Veg Oil etc do, once above so many litres/annum).
Interestingly, with diesel fuel in a diesel vehicle - there is a great movement suggesting adding 2 stroke oil makes a huge difference to the running of the engine, post 'ultra low sulphur' fuels, which suffer from a lack of lubricity.
The recommendation seems to be about 300ml 2 stroke (best to use Green stuff, for obvious reasons, and mineral based), per 60-70ltr tank.
I've tested it on my own vehicle and it does make a huge difference to the operation (not so much in terms of power output, but makes it smoother, quieter and a LOT less smokey under heavy load). Google it!
Might be worth looking in to if you are worried about lubrication on a diesel engine running A1.
Last edited by T.R Haychemu; 18th September 2013 at 17:47.