95 Civic EX. Checked my oil after 8 hours of driving the day before, and no oil came up on the dipstick. The coolant overflow tank was full above the max level, but the radiator itself was low. Couldn't see any leaks, so I'm assuming the oil burned off during the 500 miles of driving, since the oil level was fine about a week ago. I'm thinking head gasket, but only because everything else it could be has been changed already (thermostat, radiator cap, coolant flush). Any thoughts?