It has been on the tele a few times, apparently some supermarkets were
cleaned out of cooking oil. Reported that it produces a characteristic
aroma. Personally I'd initially try say a 25% blend and adjust upwards from
there. Let us know how you get on, from Pentonville if necessary.

It''ll run OK on a 50:50 mix of oil and diesel. Just make sure that no
water enters the system. Supermarket oil is good as it is water free.
Look for a small amount of dark liquid in the bottom of the bottle. If
you have a cat fitted, you probably won't be able to smell anything.
You can go to the next stage of running on pure oil but it requires a
certain level of knowledge and mechanical fiddling. Have a look at
www.veggievan.org and http://journeytoforever.org/