Well on thursday we had a customer come into our shop with a 90' F-250 with the IDI 7.3 Diesel. So the guy wanted to switch over to full synthetic engine oil and we sold and installed Mobil Delvac 1 5W-40. The guy came back this morning and wanted to go back to dino because of a couple of leaks that sprang up around the motor. I figured that I would clean out a 5 gallon bucket and then drain the Delvac 1 into the bucket. Since the oil was installed on thursday I was thinking I could possibly just dump this oil into my 91 F-250 with a 460 since I will be doing an oil change in the near future. Does anybody think this is a good Idea or something I should avoid?