Use a steam plasma tube. A 50x0.5cm steam plasma at 4 atmospheres produces 300kW of heat: use the electrics from a fluorescent light to start the plasma off. It will use3.5x10-21cc of regular water a year.
Build the car with a spring loaded 5cc water reservoir, and never worry about filling up again.
The cheapest way to turn heat into power is a thermoelectric system – BMW are looking at. No CO2, and no petrol or diesel. Read Small Generators For Sale - UK - Domestic & Commercial Purposes
So we drive cars and lorries with no CO2 – and that is 40% of the world CO2. We use such a system to provide heat and power for a house. Read http://thermoelectric-generator.com/
But these people do not realise a steam plasma tube is an excellent, carbon free heat source. So we aim to generate 50kW at home. And the national grid with pay us 40,000 UK pounds anually for our excess current.
For the car, 8kW will drive a fully laden 4 door saloon car up the motorway at 100 miles per hour. The 70mph speed limit only applies to petrol and diesel cars.
So we produce 12kW. If we go for 50kW, we can drive our own, carbon free helicoptor. That uses so little water, we will struggle to measure it.
Here are the chemical equations
1 nH++e- ->(q+1)n0 the plasma turn the hydrogen nuclei into groups of protons. qH+=p-.(Q+1)n0 – protons bonded to 1 or more neutrons
2 16O2++4n0 ->8rH++6e- the oxygens fission into hydrogens
3 H++r n0 ->Er3 carbon 0 massive free energy
4 H2O->10Er3 Er3=300kW/m