compression test question
 

I have a quick question. I am going to do a compression test and then do one adding a few squirts of oil in each cylinder. In hopes of determining if my oil is coming from the north or hopefully not the south. My question is the one spark plug I pulled out had runny oil on it. Will that oil already present in that cylinder negatively impact the test? Or is that why I have to warm the car up correctly? Thanks again.

I imagine the existing oil would prevent you doing the "dry" part of the test on that cylinder, but hopefully you'll still learn quite a lot about the enine's general health. Don't forget to have all sparkplugs out and throttle blades propped open and battery not getting low during the test.

If the plugs have oil on them then 90% chance it is valve guides. The rings would have to be really pouring oil past them to get up to the plug.