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Depends on the grade of fuel (higher octane means improved mileage), the road conditions, the number of miles on the engine, the driver, climate, and several other smaller factors. Number one: you say it's a 2008 so I'm assuming it's pretty new. A "broken in" engine will return slightly higher fuel efficiency than one than only has, say, 900 miles on it. That's a very new engine.

With only 90 miles on the odometer, it is way too early to judge gas mileage. To begin with, you probably had the truck idling for half an hour while you were checking out the interior and/or the engine bay.

Change the oil pretty quick too. It was assembled in South Korea, probably about a year ago, had a few cold starts during transit in very humid environments.

Bro you should be getting 17city & 21highway im assuming your the 2.7 Liter V6 all wheel drive since you say your not flooring it hmmm??????? with rougly only 4000 miles on the odometer right oh as for the cold stage bro if your vehicle is just sitting there idling it shouldn't take more than 5 minutes to reach its normal operating temperature remember the faster you drive your car the quicker the engine heats up also burns more gas so yeah if your driving and your engine hasn't reached its normal operating temperature yes it will burn more fuel quicker to get to its normal operating temperature have you had an oil change yet i mean your suppossed to get one every 3,000 miles yes get a full tune (especially changing the sparkplugs) that will improve your mpg take it to a technician