It takes very little coolant loss to have a bad head gasket. Ask me how I know. I am not fear mongering either. Take it to a Ford dealer, get it on record and start watching coolant levels.
Whoever told you to avoid highway driving was wrong. You should vary rpm's. That's easy to do on any highway. I would be concerned about a quart of usage. Maybe you need to take it out and run up the tach hard. Babying a new car is not necessarily good. Running the hell out of it is not...
I have about 7700 miles on my GT, with the faster A10. I've clearly noticed that, so far, the more miles it's been driven, the more power the engine puts out on my butt dyno......the most expensive dyno there is, BTW.
Anyone else notice this correlation of additional miles and performance...
Put some more premium gas in it (only thing to use) and ran the fk out of it. It likes that and I like that with my new Valentine 1. Of course I do that where "they" aren't.
No, they won't void the warranty unless you use a lame dealer. I put a much less costly J&L in mine and it works fine. You pay for the for the Ford name and plastic parts.