He was filtering very crudely, then blending in the truck.....he then switched to a better process......but still just blending settling and filtering......I am not sure when the damage occured, and I am unsure it is fuel related.....1 engine he ran out of antifreeze, and drove it tell it lost power......then it has been acting up ever since....the other engine doesnt start for crap, but it has 400,000 miles on original injectors, again, can't blame his fuel for that either......he does not take care of his trucks....just drives and drives and drives and drives.....once went 40,000 miles on an oil change, and he ran with no air filter for months......still made it to 400,000 miles untill he had an issue.