'03 Silverado Oil Leak / Antifreeze Problem

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My '03 Silverado has 67k miles on it. When I change the oil (running full synthetic) and I drive the truck, when I park it it leaves a spot of oil on the driveway about the diameter of a softball. I get under the truck to check it out and the oil is leaking on the passenger side from around the top of the oil pan. I checked the pan bolts and everything is tight. I think it is leaking from somewhere above the pan. Anyone else have this problem? Any ideas where it may be coming from?

Also, I have a problem with anitfreeze disappearing. I fill it up and after a couple thousand miles it says "low coolant" in the display. Sure enough, I buy some of that $20 antifreeze to pour in it stops the display and it's only usually about 1/4 gallon low. I can't find a single place where this is leaking and I don't have any steam in the exhaust that would signal a bad head gasket. Anyone know what's going on? Where is this antifreeze going? Oh yeah, the dipstick is clean and there doesn't appear to be any in the oil.

Please help guys and thanks for the input.