It smells and its sticky, heavy, dirty and some people will laugh at you. Put off yet? No?, then read on.
The oil gets thicker as it gets colder. Vegetable oil is thicker than mineral diesel at room temperature, that's why we have to heat it before we can put it in the engine. At lower temperatures it can even congeal (as does diesel I might add). So this is taken into account with the design of the conversion kits and you don't really need to worry about it unless we get a spell of particularly cold weather. In that case you'd do the same as you do with diesel and heat the fuel before setting off down the icy road or thin it down with either mineral diesel or another suitable solvent (consult the handbook/car manufacturer). In the UK we will very rarely have this problem so it's not worth dwelling on it too long.
The smell I find this is a matter of attitude. Picture yourself about 10 yards outside the doors of a fast food burger shop. The smell you get there is the same as standing right by the back of the car next to the exhaust pipe. If you're not offended by this then that's OK. I've noticed that unless people are aware that you're running on vegetable oil they won't notice the smell of the car and certainly won't link it with the car. I live in the countryside and so the smells left along the road quickly dissipate on all but a deadly calm day.
I like the smell - it's interesting how your attitude towards the smell of mineral diesel changes when you've been running on vegetable oil for a while. Mineral diesel will smell harsh and acrid by comparison. I also wonder if there are some bright chemists out there who could help me with flavourings for oil. Please get in touch.
Handling Clean new oil is the simplest (and most expensive) form of the fuel. You buy it straight from the supermarket or wholesaler and pour it from clean containers into the tank the same as diesel. There are a number of people on the continent who have set themselves up with a bulk container in their garage and they dispense the oil through a 'petrol pump' nozzle. It costs about £500 to set up a tank like this but I haven't found a bulk supplier who'll come and fill this in the UK yet - If you're a supplier then get in touch with me. At the time of writing this I'm close to finding a source so e-mail me if you need details.
Other people's perception This can be both a positive and negative thing. There's a chance that people will think you're mad but a few of the well chosen comments about sustainability and the environment usually keep them quiet. I think the difference of vegetable oil, made obvious only by the smell is an advantage and distinguishes this from any other fuel.