I've got a 1998 FL50 with Cat 3126 and Allison with about 31,000 miles. I keep the coolant just above the site glass. I've recently -- over last few months -- noticed that after 1000-2000 the coolant drops just below the site glass. So I pour in a 1/2 quart or so. I don't see any leaks around any of the hoses or on the concrete pad. Engine runs fine. Just curious if others would consider this normal or if some problem deep inside the engine is lingering. I will be keeping an closer eye on the coolant usage.