When pulling up to our very first gas station, on the highway in The Netherlands, we were extra sure not to pull up to a Diesel pump by accident. "There, that one says 'gas'!" I pointed out to Merlin.
We both immediately remembered our friend Lukas, in Amsterdam, telling us about natural gas pumps. Fuel is very, very expensive in Europe and a lot of people opt to convert their car's systems over to run on Autogas (basically 'propane'). It costs a lot to make the switch, but it saves a lot of money in the long run. Autogas costs less than half what petrol does and 40% less than diesel. Also, the carbon emissions are much lower, making it a more environmentally friendly option. So far, we've seen them in Holland, Belgium, Luxembourg and Germany. How amazing that we had never even heard of it! Even more amazing that the option exists. Good job, Europe.
Update: Autogas is also big in Australia and parts of Asia.