I don't know what to make of this business of detetergent oils loosening old sludge.Lots of sludged up engines out there ,even ones run their whole life on detergent oils. Once Bought a used a 84 Cherokee, when I removed the valve cover, the crud was so thick it left an impression of the valve cover, like a jello mold.Couldn't get that cover back on fast enough, and ran the Jeep for 4 years like that.I changed the oil pretty regular, so why didn't the sludge move??(it didn't). Had to pull a gutless 2.8 engine on a 83 S10 once to repair an Exxon Valdes class rear main leak.Pulling the pan was like winning the sludge lottery ,Yuk.Why didn't my regular oil changes on this sludge left my the previous owner,loosen it up and clog the oilways? Oh, the rear main leaked when I bought it, got tired of slipping on the oil slick on the ground.Is detergent sludge different than non detergent sludge? Have any of you actually seen an engine ruined by terminal sludge movement caused by switching oil types? I mean you could absolutely, positively, say it died from displaced sludge, not just simply gave off blue sparks and smoke because it was a bearing rattler to begin with.
