In the late 60's I had a '60 or 61 Econoline van. It was an ugly beat-up thing with the 170" engine. I changed the oil regularly but have no idea how often the prior owner did, or if it he ever changed it at all. Once when doing a clutch replacement I dropped the pan for a looksee. There was about 1/2" of heavy sludge crud buildup on the main caps. I just buttoned it back up and kept driving it.
