Hmm, 'tis a subject that occasionally grabs my attention. Yes, I think its a good idea to reuse old cooking oil to make a vehicle fuel but I keep coming to similar conclusions. Once every chippy/burger joint/whatever is having its old oil processed into fuel, what then? As has been mentioned on some radio chat shows recently, crops get to be grown specifically for sale as fuel which in turn hikes the price of the foodstuffs that the crop originally went to satisfy - before too long everybody is paying more for everything, because of the taxation associated with fuel.
There was a scam not so long ago where folk were buying huge ammounts of cooking oil and running their cars on it without any modification, there are also people who blend anything from cooking oil (whether used or not) to farm/marine/central heating fuel.
I really think that it comes down to - if you want to get a few more miles to your pound, get a more economical vehicle or be prepared to travel more wisely - though sticking to this maxim is very difficult indeed when you are used to the convenience of speed and comfort that we all know today.
Incidently, at the Smallholders Show yesterday at Builth Wells, a company were selling Bio-diesel at £1 per litre, now I know that pump prices are only just below that, but unless I become a tree-hugger, that strikes me as expensive, when they have recovered their base comodity as a "waste" product.
I have a much wider view on this subject but it'll turn into a rant so I'm stopping right here.
Ogri the trog
