Biodiesel from waste oil is an excellent technology, reducing our usage of mineral oil and dealing with a waste product. Biodiesel from virgin oil is a dead-end, using large areas of food-producing land to produce small quantities of fuel.

Also you don't necessarily have to convert to biodiesel - my old Peugeot ran quite happily on up to 10% filtered waste veg oil during the summer months in the UK (low winter temperatures make the mix too thick, so storage for summer use is better). Whether running SVO/WVO or biodiesel, check carefully that the pipework in YOUR vehicle is suitable, as certain tubing can be attacked by VO and biodiesel.

Of course the number 1 tip for environmentally friendly transportation is reduction - support your local farmers and buy local, walk where you can, phone meetings rather than physical meetings and so on. Simple, boring but effective.

Off topic, in reply to previous posts:
Comparing known reserves of natural gas, oil and uranium, at the current (low) rates of usage uranium has around 65 years reserves, compared with 62 years for natural gas (which is HEAVILY used at the moment). If you want to expand nuclear power a little bit, say doubling it (note, this small amount isn't going to save the environment!), then the 35-40 years reserves of uranium at that level compares with the 42 years known reserves (current usage rates) for oil.

Nuclear power isn't renewable, nor is it capable of meeting our expanding energy needs. Even its proponents only make claims for its potential as a bridging technology, until real renewable generation can take over. The time and energy invested in the nuclear industry would be better spent on developing properly renewable energy sources.

Moving on to disposal, techniques for dealing with the smallish levels of high-grade waste have improved hugely over the years, and with vitrification and synroc, there IS a realistic option for long-term safe(ish) disposal. The volumes of MEDIUM and LOW grade waste, however, dwarf the high grade waste, and for these there is no long-term solution, just bar-talk ideas such as reincorporating within uranium mine waste and reburial or injection in subduction zones.

Nuclear energy CAN appear to be low-carbon looking just at production, but whole lifecycle analysis, including storage, disposal, research, monitoring and decommissioning significantly changes this picture.

Fusion technology, though, is certainly worth further research.