cornbinder89 wrote:In my long career as a mechanic, I have never seen an engine lost to the switch to detergent oil. Detergent oil doesn't "scrub" the inside of the engine, rather it keep dirt an muck in suspension so it can be removed by full flow filters. Older engine didn't have full flow filters, so the bottom of the sump was where most of the junk ended up. Non-detergent oil allows the heavyer stuff to drop out. I'm not saying it can't happen, but that I've never seen it happen.
When I bought my 1957 Ford tractor it was holding 40 psi with no smoke,and I couldn't figure out why the landscaper that sold it to me (young guy) had put it up for sale and bought one of those new little dozers with the arms that lift the bucket overhead.
I mostly used it to pull and power a bush hog once every couple of weeks,or to move stuff around in the yard,so it took a while for the oil pressure to drop. It gradually dropped down to around 5 psi,and I figured I needed crank kit and the previous owner had STP'ed it to death to get oil pressure to sell it.
Since I needed to use it right then I decided to just change the oil and filter (both looked new when I bought it) and see if that helped. When I unscrewed the oil filter from the side of the block it was so heavy I couldn't believe it. Evidentially the previous owner had changed the oil and filter when he bought it,and panicked when the oil pressure started dropping,and then changed it again to sell the tractor because once I put a new filter on there and filled it with 30wt non-detergent oil,the oil pressure went up to 50 psi at idle warmed up. It started to drop again after running it for several hours,so I just changed the filter again and added a quart of 30 wt non-detergent,and haven't had a minutes worth of trouble with it since.