Recently, diesel engines in general became more and more sophisticated, using the latest achievements of the electronical and metallurgical revolution of this decade. These efforts, mainly involving chamber diesel engines in light duty applications were however hit across the face by a sharp cut in public acceptance of the diesel engine due to its traditional drawbacks and due to close competition with even more advanced and clean gasoline engines.In order to overcome that disastrous situation for the most fuel efficient diesel engine, the authors suggest to of course accept sophistication wherever possible, but to think as well about the big steps which still are necessary. Such steps were proposed already in earlier papers (1, 2, 3, 4)*, meanwhile backed up by the experience of intensive testing and start-up of serial production, and involve the following features for small to large-sized direct-injection diesel engines: 1. Cooling the engine block only from the interior and totally eliminating any water or air cooling. 2. Eliminate soot at up to 16 bar B.M.E.P. With a corresponding reduction of diesel particulates. 3. Give the engines multifuel capacity to run not only on mineral fuels (such as methanol, gasoline, diesel oil, heavy oils), but also on the environmentally safer and renewable fuel that vegetable oil is. 4. Eliminate the CO2 pollution by saving energy and by using vegetable oil as fuel. The plant takes from the air in order to produce that fuel all the CO2 that is returned to the atmosphere when the fuel is used. 5. Improve at the same time the power, torque and fuel efficiency of the engine while reducing combustion noise and exhaust pollution with CO, HC and NOx. The means to obtain this are a duothermic, isophone, two-jet d.i. combustion in combination with an articulated two-piece piston with ferrum crown and a redesigned cooling system.