Stupid me. I changed the oil on the '88 Cherokee yesterday. I was looking forward to seeing how the Rotella T 5w40 was doing in there. I finished the oil change a put the bottle on the shelf next to the shipping container. Went back to the Jeep and did a tranny fluid change and rotated the tires, as well as some other stuff. I went to grab the sample to package it up, and promptly knocked it on the floor where it exploded all over. Of course, taking it out of the oil pan is asking for skewed results, especially when mixed in nearly equal parts ATF! RATS! No Rotella T 5w40 sample for another 4 months... Sorry for the delays - I know we are all having fun seeing what these oils can do in the 4.0!