The XT has a towing capacity of 3500 lbs with a properly installed class 2 or 3 hitch. I strongly recommend a class 3 2" hitch and receiver. From previous experience towing in other vehicles, that weight should not cause major problems beyond the usual consideration for making sure the load is properly balanced (tongue weight somewhere between 100-200 lbs is a reasonable starting point), making sure you don't try to accelerate too fast, braking and slowing down earlier than usual, etc. As for wear and tear on the car, you'll be "in the turbo" a lot of the time so higher octane fuel may help prevent overheating. I have found that the outback CVT transmission likes to hunt a lot even with gentle hills so you may see the engine RPM surging a bunch depending on your speed, driving technique, and hills/mountains. If that happens, consider going to manual mode and downshifting until the car is able to hold speed without needing to floor the accelerator. Also keep your top speed lower to reduce drag and strain on the engine. Towing wears cars out faster, no matter how you do it. Proper maintenance (oil changes, brakes, etc) can help a lot so don't start a long trip with a trailer if you delayed your oil change past 4000 miles (for example). When I was towing a lot, I would change my engine oil every 3000 miles just to try to reduce engine wear. If you're going to tow anywhere near 3500 lbs, make sure you get a good class 3 tow hitch receiver installed and a properly rated drawbar and ball. I paid extra (and waited 8 months for delivery) to get the real factory tow receiver installed, but any appropriately rated drawbar and ball should work so don't pay hundreds for the ridiculously overpriced subaru drawbar. Finally... People in other countries tow HUGE weights compared to what is legal in the US and they do just fine. As long as you drive carefully and keep the load properly balanced, 3500 lbs shouldn't be a problem behind an outback. Yes you'll be causing wear on the motor because the turbo will be working fairly hard but if you keep your speed down the trailer you're talking about is well within subaru specifications and should be fine.
