>>>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.
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>>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!
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>That would make me really nervous. Nothing in there is going to gunk up the engine?

Like I said, they've been doing it for a number of years now, and so far, they still are, so I assume they aren't running into any major problems. I guess it depends on how well you clean the oil. You also need either a newer (after about 2000) car, or you need a bit of an overhaul and some conversion. From what I understand, in the older diesels, the hoses etc can break down under that type of oil.

Have a look here