I took my v6 with 72,500 to Ford after noticing a strange hissing in the engine. On the way to the dealer I noticed that my car would struggle at highway speeds. After a few days they tell me that the engine is misfiring and that their is low compression in 3 of the cylinders. The cylinders are all on the same side, ones down about 5%, ones 8% and the other around 13%. I also noticed my coolant level drop about 3 weeks ago when I went to get an oil change, but no leaks/pools in my garage. Could coolant be leaking into my engine? Could it be a bad head gasket? I did the oil change maybe 2–3 weeks ago and my mechanic didn’t notice anything strange except the low coolant. He just added water because I told him I’ll be taking it into the dealership for its 60k mile service (i know I waited over 10k miles to do it, could that have caused issues?). Ford did a quick drivability test but couldn’t tear it apart until 2 weeks as they are super busy. Decided to take it to a mechanic my uncle trusts but wont check it till Monday. Just wanted to get some ideas on what could be wrong.