A local farmer re-processes his lubricants through toilet paper using gravity and some heat with good lab verified results. He pointed me to an article where someone built a similar but much smaller contraption to do the same thing. To add extra oil to his system the farmer's sons change the oil for several neighbors that use Mobil 1. They buy their Mobil 1 at Wally World and get free labor, the farm gets the used oil and puts it through the process. If the oil passes a viscosity test it goes into the pickup trucks and other gas engines on the farm. This oil makes it through about 3 of these cycles before it's finished and passed on to the recycler in town. This is a project run by two brothers aged 10 and 12. They maintain the gas engines (pumps/generators/pressure washers etc) and most of the routine maintenance on the 12 pickup trucks. All the pickups were purchased new and are 1949 to 1968 vintage. It is said on this farm that the pickups will only be replaced when they're worn out and can't be fixed. They are not impressed by newer pickups with a/c, automatic transmission, fancy interiors and modern electronics. They change oil in the pickups based on a schedule of gallons of gasoline used. They say when the pickup uses more gasoline it's working the oil harder and that determines the interval. They say this compensates for periods of idling and slow driving in the fields as well as running down the highway at higher speeds. They use farm gas which has no corn in it and they dose the tank with Chevron PEA additive and filter the gasoline through, you guessed it, toilet paper.