1969 C10 8/350 coolant usage

[Sven]

One question I have regarding coolant use. I fill her up, doesn't seem to leak at all, the exhaust isn't an unusual color and there's no coolant in the oil but the coolant level drops during use. I've replaced the hoses, rad cap and thermostat and she runs pretty cool. Well, unless I let her run out of coolant.

What do you think? Anything I should be looking at? I know she's an old lady and deserves to be a little demanding at times, but I don't want her to hurt herself.

-Steve