Re: 2009 AWD 100k 13mpg??
I think an intake cleaning, new plugs, and a new air filter will probably help your MPG the most at this point. If you're not already doing it, adding a fuel system cleaner at a consistent interval will help things out, too. There are plenty of people here that use only Tier One fuel and add Techron (or similar) at every oil change. I use only Tier One fuel and add one can of BG44K once a year and I've not had any issues. Your mileage (and the opinions of others) may vary.
We just did 100K maintenance on our 2010 back in November/December. This included new plugs, intake cleaning service (1st time), transmission flush (second time), and coolant service done at the dealer. We were seeing between 14.5 and 15 MPG around town, but high temps had been around freezing and lows were below zero. After the service, MPG was between 16.0 and 16.5 MPG around town (back to where it had been in colder weather) and we averaged over 21 MPG on our 1600+ mile Thanksgiving round trip--I think the intake clean and plugs were probably the keys to that improvement. That trip was with a fully loaded vehicle, lots of mountain driving, some in-town driving mixed in, and fairly cold temps.
I also did an oil change, air filter change, transfer case/rear differential fluid change (2nd time), front brakes (1st time), and serpentine belt (1st time) before we left on our trip, then replaced the factory struts/shocks after Christmas.
100K maintenance can be expensive, but worth it if you're keeping the vehicle for an extended amount of time.
2010 Traverse LTZ AWD<br />Born 11/09<br />Silver Ice Metallic, Titanium Leather<br />DVD, Nav, Sunroof, Towing<br /><br />Just drive it.