Green or Mean?

For some time now I have owned a very small and some would say stupid car; a Ligier Ambra.
It is green in colour, and as it only has a small 505cc diesel engine, i would argue it is also green by nature. It takes up less than half the space of say a Ford Escort, and is recycleable, it also achieves almost 80 miles per gallon.
The drawbacks of a maximum speed of 40 mph and space for only one passenger pale when you realise this is only used for commutting - my journey is 10 miles each way and only I travel, so my 7 seater stays home and I use this pod. The people carrier costs about 12 pence per mile in fuel costs, the pod costs just 6 pence per mile. Enough said.
However, it's not green enough and is costsing too much money to run! I took out the spare wheel to save weight. If I get a flat I will have a maximum of five miles to walk either to work or back home. Big deal I can cope with a five mile stroll once in a while. Still costing too much though.
But not any more. Now i have converted it to run on Vegetable oil. The parts to convert cost £40, which means in a months time i will have paid the conversion cost and start saving. Diesel is 95 pence a litre, Vegetable oil is 49 pence a litre - almost half the price, or if you prefer about 2.8 pence per mile. Now that is seriously cheap motoring. Even better, I'm going to buy some filters then it's downto the chippy to beg their used oil. That'll be seriously FREE fuel.