[Brian R.]

And here is an explanation for the sludge occurance by fxashun (one of the instigators of the sludge problem discussion):

I asked our buyers and techs why this happens and here's their reason. When Toyota went to 2.2 liters from 2.0 in the Camry for some reason it caused the engine to run hotter in the upper cylinder area. This breaks down the oil faster that the recommended oil change interval allows for. If a Camry is cared for "by the book" there is a very good chance it will probably have sludge. If it has oil changes every 3000 miles or so it should be OK. It's just that many people don't.

Sludge can be checked in the Camry by looking in the oil cap because it screws right into the valve cover. It is not necessary to pull the valve cover in the 4 cyl. Camry to check for sludge because of this. You can actually look into the oil filler and see the insides of the cover. If the filler was in a remote position or covered as on the V6 models you WOULD have to remove the valve covers.