Engine Mechanical problem
1996 Cadillac Deville 4 cyl 188000 miles

I HAVE TO KEEP PUTTING WATER AND COOLANT INTO MY RADIATOR BUT THERE'S NO LEAK. IT OVERHEATED A FEW TIMES AND THAT'S THE ONLY TIME I'VE SEEN A LEAK. THE HIGHEST MY COOLANT LEVEL EVER WENT TO WAS 222 NOW IT WOULD GO UP TO AT LEAST 250 AND THEN GRADUALLY GO DOWN. WHAT IS THE POSSIBILITY THAT IT'S MY THERMOSTAT. THERES NO WATER LEAKING BY THE WATER PUMP THE ONLY THING I NOTICE LEAKING IS THE OIL.

I would definately change the thermostat first. That would cause the problem you describe. And it would be a cheap fix.