If it was not for bad luck I would have none at all!

You can tell everything you need to know by doing 2 things: 1 Check with mechanical gauge as stated above by others. 2. Pop off the easiest side valve cover. Trust me...The sludge will be quite evident under the Valve cover if it is indeed a "sludge motor". You can buy years of driving time by just cleaning the screen and replacing the oil pump. PM me if you want to talk more about it.