Just recently my 07 decided to start Swallowing gas. On a full tank of gas by the time I get to a half tank on the gauge my trip meter is showing roughly around 60 miles driven., while the digital dash is showing around 180 miles left. Any idea whats going on or what it could be? Both my Cats are bad, but I still cant see using a half a tank in only 60 miles.

 

Few of things.

Do you have any codes?

If your Cats are bad, how come? Have you been dumping fuel into them?

Leaky injectors?

Sending unit might be malfunctioning. Drive on a full tank and when it drops to half and you have only gone 60 miles. Fill it up again and see how many gallons went in. If only 2 plus gallons went in then I would guess your sending unit is needs replacing.

 

Check out the temperature of your rear brakes after a long drive, if it's way hotter than the front, your rear caliper has seized. Replace the seized caliper with brand new OEM one and you will get your MPG back to normal. Don't go with aftermarket or refurbished one, they will seize again pretty soon.

 

Might be an easily looked obvious thing....did you check your tire pressures as they may be low.

 

How do you know the CATs are bad?

A sanity check would start with inspection of the air filter, replace if dirty. Clean the MAF, the engine needs to know how much air is moving through it. Inspect and listen for vacuum leaks. Get your hands on it.
Because you mention poor MPGs, bad cats, you might want to inspect/replace the spark plugs too. If the fuel isn't being burned it could explain both of these.

Start there. Also, if the cats are plugged from burning unburned fuel they will restrict flow and the engine won't rev. So they will also impact fuel economy. You need to know why they went bad.
GL