I just came back from a 2,500 kilometer trip towing one of our camper trailers with my uncles Outlander. It's a 16 foot unit that weighs 2,000lbs dry and roughly 2,700 loaded up. We went well over 2,700lbs as we had a generator, lots of equipment, full tank of water, overstocked fridge, luggage etc. We started off in Calgary, AB and went to Vancouver, BC. I only filled with Shell Premium. It's a 60 liter tank to my knowledge and WOW, the range sucked! I had to fill up every 250 kilometers!! And it cost well over $75 each fill. That means I had to fill up 4 times to do 900km!

My least favorite part of the trip was the transmission. With the V6, we all know it comes with the 6 speed auto. Well I wished we had the CVT. It could not make up its freaking mind! I put it on cruise on a very flat road with no wind, and it stayed in 5th for a bit, then 6th, then all of a sudden...3rd! then 4th, then 6th, then 5th then 3rd again! This kept going on and on! I eventually took advantage of the paddles and found 4th gear to be the best, revving at nearly 3,200rpm, it had a bit of torque for small hills but still maintained low enough RPM to get decent fuel mileage(more on that later). Power was never an issue, even going on the mountain roads, thankfully, but I just wanted to shoot the person who came up with the brain for this transmission.

Comfort was somewhat of an issue, this car was a fully specced out GT model and it had no lumbar support! My back was aching after an hour. Suddenly the pitiful range seemed like a good thing so I could get up and walk. Other than that, the ride was nice, space was awesome and features were abundant. One tip if you're towing with these cars...USE STABILIZER BARS! I tried towing without them, and the trailer swayed almost dangerously and the car squatted badly. Also, engine temperature was never an issue. I kept a close eye on the ECT guage and it didn't budge a bit over the most strenous mountain road doing 6,000rpm full throttle for 10 straight minutes(The A/C was still blowing ice cold)

Now for fuel economy, I was hoping for 15-17mpg(US). Nope. Over the whole trip I got 14. For all the fill ups heres the temporary fuelly account: Uncles Outlander (Mitsubishi Outlander) | Fuelly

We have a Ram 3500 with the 6.7L Cummins and a 25 foot fifth wheel trailer and we can easily get 15.5mpg in the mountains fully loaded. But then again, this little engine had to work quite hard.

So after all this, my unbiased opinion is, for towing, this isn't the most ideal rig. I tried an Escape 2.0 Ecoboost a few months back and it was much happier towing the same load and fuel economy was a tiny bit better, albeit it was on flat roads. I like the Outlander and sure, it's capable of towing 3,000lbs, but for the love of God, avoid it.

 

I have 2010 v6 outlander, not a GT and I get approx. the same mileage when I pull my trailer around mountains. On the flat, I could probably get around 15/16 ltr/100km.

I also found that I get slightly better mileage when I put the transmission in manual.

 

First, holy crap you didn't use an anti-sway hitch???? For your fifth wheel, you don't need it because the pivot point is right above the rear axle, you inherently have no sway. For bumper towing, any load which is essentially a big sail needs an anti-sway hitch. Especially with the soft rear suspension, because less weight is on the front steer wheels, you have even less control. It was very dangerous to drive as you did.

Get some airbags for the outlander, this is only $100, just use a bike pump or tire air compressor to fill it:
2007-2012 Mitsubishi Outlander Air Suspension Kits - Firestone 4182 - Firestone Air Bag Suspension Kit

That will eliminate the squat and give you back control of your travel trailer.

Second, get an anti-sway hitch, the hensley cub is the best for this application, you won't even feel the trailer behind you:
The Hensley Cub
The hensley cub is about $3k, but well worth it considering the outlander is a marginal tow vehicle. If you had a large half ton pickup i'd say just get a regular anti-sway hitch.

 

My bad, I should've clarified it. I have stabilizer bars and the proper hitch, but I had to hook the trailer up and move it 10 minutes down the road. For that small trip, I didn't have the bars on. For the long journeys, I had them on.