My brother bought a 92 Chevy van with 138,000 miles on it. He brought it to me hoping that I could give it a once over before he started to use it. I checked the oil and it was low and black. I looked underneath and the filter was an AC Delco that looked old and covered with crud. I changed it with 4.5 qts Havoline HM and a Puralator filter. Any thoughts as to how long I should have him leave it in there? I think 3,000 miles may be right for the first one. Then possibly longer. When I drained the oil it was jet black and there was only 2 maybe 2.5 quarts in there (including the oil I drained from the filter). Recommedations welcome from people who have the 4.3L.