After test driving for 100-miles and a mechanic's inspection, I purchased a 1993 Lincoln Town Car with 225,000 miles.
With the first oil change, I suddenly noticed billows of gray smoke upon taking off from an intersection. Apparently, the previous owner filled the crankcase with some sort of Motor Honey to hide seal and valve damage.
I had a compression check done . . . the rear three cylinders. 6, 7, and 8, showed low compression down around 20% average. #6 reached full compression in the Wet test but was down almost 33% Dry suggesting piston ring problems. One mechanic suggested a rebuilt motor, another a new intake gasket . . . I decided to have the EGR valve channels cleaned and run two Auto-RX treatments through two oil changes and three oil filters.
After 6000 miles, the smoke was gone . . . period. The motor runs fine except for some valve ticking from one cylinder on starting the motor in very cold weather. I may try one more Auto-RX treatment just for good measure.
For $45 and a $125 compression check, I saved thousands in repairs.