>The latest European diesels are absolutely amazing. It's possible to burn used frying oil in a diesel as well should the price of fuel continue to rise.

People have been doing that here (and in the U.S.) for a few years. It means pretty much running the car on free fuel. Restaurants have to pay to have the used oil carted away, so they're more than happy to give it away to anybody who wants it. Diesel drivers have been taking the used restaurant oil, cleaning it and fuelling their cars with it. Talk about cheap fuel!