Contour Enthusiasts Group Archives Forums General Troubleshooting cats just replaced; any reason to change oil/filter?

Well since the cats are in the exhaust system any crap should be pushed out the back end.
I don't think turbulence could cause crap to go up to the exhaust valves and into cylinders since it would have to fight gravity and exhaust gas pressure. If it did of course you would have scored cylinders, valves and valve seats, and possibly bye-bye engine.