From 1930 to 1987 the Lister company made diesel motors for pumps, generators, and general-purpose use, using mostly the same design of big, slow-speed, heavy flywheels and simple, easily-repaired parts. The Lister company then sold the designs. Today there are many Indian and Chinese companies that produce Lister copies (aka: “Listeroids”) for export. These are fairly faithful to the original design — with varying quality. The price for these engines *per kilowatt* is cheap, when compared to the more commonly found gasoline-powered generators, though they are not very portable. What is truly amazing is the efficiency of the Lister: one user reports an average of 8000 watts and gallons of diesel per hour. They can be made nearly silent with cheap car mufflers or a water muffler. They run fairly cool, and home-built radiators (water tanks, house radiators, car radiators) seem to work well. These slow-rotating workhorse machines are good for nearly 100% duty cycle if properly maintained. (A 100% duty cycle means running 24/7, with no down time due to heat and lubrication needs). The Listers can run all the time, and there are even some people who have figured out how to do oil changes while the motor is still running, thus removing even the lubrication issues. Their efficiency and raw power makes them perfectly suited for electrical generation for long-term use versus “emergency-only” generators which have an extremely short lifespan. They are also works of mechanical art, and will keep a mechanically-minded hacker occupied for weeks, experimenting and tuning. I’m sure that vegetable oil or waste motor oil would work as fuel in these engines as well, but more research is needed.
There is a documented story of an automotive engineer showing up at a state fair booth where a guy was demonstrating an oil additive. they had a motor set up where two pieces of metal rubbed together and you could see the reduced friction when their product was added. The Engineer asked the guy running the booth if he would try 'his stuff', .... new pieces of metal were installed and this mystery concoction was added. To the amazement of the Booth Operator, he couldn't apply enough pressure to the disk to slow it down! The performance of this mystery stuff was off the chart, and clearly better than the stuff he was selling.
It is interesting to read about slow speed diesel engines verses high speed engines. Some think that the wear in an engine is in direct relationship with the travel of piston and other parts. In some design, running at half the speed produced more than four times the life. These finding are often seen in slow speed marine and power generating plants. When you want the best examples of efficiency, look at Marine Propulsion. These companies live or die according to the efficiency of their fleet and longevity & efficiency of the engine is critical. These are the same things that producers of off grid personal power should be looking at. Who knows, the Lister types may live on longer than anyone could imagine