Running on veg oil - why ?

Watch out for law changes, that still might make you a criminal.

If it is on a carb, then with rejetting and some new hosing, and seals it could potentialy run homebrewed ethanol distilled from animal feed, and some vegetable scraps.

But you need to make it as pure as possible. Methanol eats fittings, Ethanol usually doesn't. It is lower calorific value, but higher octane, so you could advance the timing. What you would need to do was find out if biomass fuel includes home distillation, like it can in other EU countries. In france farmers are allowed make and sell small ammounts of brandy/armagnac on the local markets and own stills.

If you could distill your own from feedstock, you might be able to make it cheaper.

Any petrol engine can with lowered compression run on the likes of lamp oil, kero, paraffin etc. You can buy cheap generators now on ebay that are designed for the third world that do it. Basically you start on petrol, and once warm you awap over to paraffins etc. Any low octane crap, like para, deseasel, sainsburies chip oil, baby oil (comes from crushed babies apparently??? I used to add it to model plane rocket fuel for the smell) and almost anything else including now banned creosote! Just fit a handfull of head gaskets and play! Once warmed a petrol will burn most anything if you lower the compressio loads.