Re: engine question
It is possible it is the valve seals and not the rings. A leak down test will tell. Do what jeff suggested and you will probably ok.
I wouldn't tell you to try it, but I know first hand of ppl using Bon Ami Cleaning Powder on oil using motors with decent results. I personally have seen it completely clean up a high milage oil blowby motor to the point of barely using any oil. I have also seen it used with no effect at all. I would personally use it as a last resort to rebuilding a motor, know that if didn't help you were going to rebuild anyway. To buy a truck thinking to clear it up...not so sure.
John