My friend who has a 92 CTD just got 250 gallons of fuel oil for free. We pulled it out of a house that no longer needs it. It was 3 years old. He is going to mix it with restaurant grease and diesel. He has been successful with the grease in his truck, mixing it with diesel. My question would the fuel oil say 5 gallons to 30 of diesel in my truck hurt anything? I have an 03 CTD. This guy is on the right track I believe. He now has 3 tanks. 1 with diesel, 1 with restaurant grease, now 1 with fuel oil. He runs the grease/diesel in truck, Kubota tractor, & a International truck.