I have a 1998 buick lasabre that had some work done, just oil change & tune up. Appears the tech left the PCV valve off. Overnight, engine developed low knock in bottom half of engine. It was also suddenly 2 qts low on oil, but no sign of leaks on the exterior, now engine needs to be replaced. Can running with no PCV cause this to happen? There are metal flakes in the oil when you remove the dip stick. Any ideas, may want to go back against the shop that did tune up and oil change
K

Kim,
If it is the 3800 V6 I believe that the pcv valve in that engine is under a "cover" and if not installed properly, or if the "O" ring seal is left out, the engine can and will use a couple of quarts of oil in a very short period of time, say 200 miles or less. I would take the car to a Buick dealer to verify that it is the same setup I am describing. That is the only way I can think of the engine losing 2 qts of oil that quickly. To be honest with you though, many engines have been run 2 qts low for a long time without any serious damage. I don't know all the details, such as the mileage on the vehicle, how long after the oil change the problem occurred etc.
Hope this helps,