Losing coolant

A couple of days after getting an oil change, I noticed small drops of oil in the garage where my wife parks her car. This went on for a few days then I took it back to the oil change place to see if they messed something up. The guy told me the everything looked fine with the oil, but that the coolant reservoir was almost completely empty, despite having topped it off the week before.

The spots in the garage definitely weren’t coolant, so I figured they forget to top it off and didn’t want to admit it. I didn’t notice any new drops for a few days, until two days ago when a new one appeared. That afternoon, my wife was running errands and called to say that the heat didn’t seem to be working. I checked the coolant when she got home, and it was empty again.

I read that if coolant is leaking into the engine that the oil cap will get a white build-up on it and the oil on the dipstick will look milky. Also, white smoke might come out of the tail pipe when the car is started. I’ve noticed none of these symptoms.

Thanks for your input.