1993 Dodge Colt Dodge Colt Using Oil

Engine Mechanical problem
1993 Dodge Colt 4 cyl Front Wheel Drive Manual 171K miles

I have a 1993 Dodge Colt on a second engine, stock Mitsubishi 12 valve, and my original engine of over 166K miles used nearly 2 quarts of oil between changes every 3,000 miles. The head had been rebuilt and cylinder walls honed out at 133k and by 166k, developed piston slap, and the engine was replaced with a used one with only 86,000 on it. They both ran great and the new one still does (38mpg!), But it still uses at least 2-3 quarts of oil between changes, and does not smoke, has no visible leaks, dry around filter and drain plug, and no drip spots. What could be causing this? You'd think it would be important to fix. I used engine restore on the old engine and it still used nearly a quart and a half to 2 quarts between changes. I am using Pennzoil 10W-30 if that makes any difference. Any ideas? Thanks.