Yes, I recycle oil. I have been using it in my 1988 Ford F-350 diesel with good results. I filter the oil before blending it with Diesel fuel. I'm not sure I want to try pure engine oil in my pickup, and Global Warming has sure made it a cold winter, so I have not exceeded 20% for the waste oil to avoid viscosity problems. I have used other waste oil, but it's just not available for free in the quantity as wasre engine oil.

Power and fuel mileage appear to be increased, although I have not been able to confirm this. I would worry abt using a newer diesel engine like my other 1996 truck which has computerized electronic fuel injection. Anyway, I filer the oil by running it through a coffee filter, and let water settle out if there appears to be water in the oil. Anyway, it is a slow process, so I have some 60 gallons of waste oil waiting. Anyway, a rough estimate seemed to be the pickup went from about 20 MPG, it's normal mileage, to at least 22 MPG. I had a job in Waco and went 248 miles on a single tank, a feat that normally would need a refuel at about 200 miles. I even got a bit nervous after 200 miles, fearing I would fell the surge that the engine makes when it is sucking the last bit of fuel out of the filter, but it never did, and I went another 12 miles the next day to fill the tank back up.

thats awesome. I want an old diesel one day. its on my wish list.

I believe stainless was doing this for a while too..