2011 GMC Terrain fuel system problems

My 2011 GMC terrain has a 2.4l 4 cylinder front wheel drive. It is rated at 32 mpg highway. Since day 1 I have not even gotten close to this. I drive 100 miles a day and maybe 5 miles of it is considered city driving. I am getting 20 to 22 mpg. I contacted GMC and they had me take it in to be checked out. The dealership hooked it up to there computer and said that everything is the way it should be. They then told GMC that it is winter now and fuel mileage will drop due to cold weather.

There was a recall for my vehicle to replace the high pressure fuel pump. This was replaced and 1 week later the check engine light came on. Taken to dealer. Diagnosed as catalytic converter. The catalytic converter is under a public service extended warranty (10 years, 120,000 miles whichever comes first). Of course I now have 138,000 mile on the vehicle. GMC will not cover repair costs. This should be a recall not an extended service warranty. The vehicle was moving when the light came on.