At 8000 feet is there a difference between a 4 cylinder 250 hp turbo and the same car with a 6 cylinder also 250 hp without turbo (presuming all else is the same)?

Followup to JS08016 I guess I was thinking in terms of peak performance. If I were to accelerate up a steep slope at high altitude, would one or the other engines perform better, or would it be, as you say, fully compensated for by the computer. My theory is that the turbo, by compressing the air, would do better than the 6 cylinder engine. The other thing I didn't really factor in is that a Turbo is lighter than a 6 cylinder engine... but let's just say the Turbo has added dead weight in the front passenger seat to compensate.

The forced air would definitely have more power than a NA engine.

I'm glad you asked this question. I have a 2010 Subaru Outback 2.5 with the CVT transmission and took my car and tear drop trailer which weighs about 1,000 pounds to the North Rim of the Grand Canyon, elevation, 8,800 feet. The car worked just fine and I got excellent mileage on this trip. The difference in towing capacity on the H6 and H4 is 300 pounds. If you really need the two seconds of acceleration on the H6 and don't mind the extra money for gasoline, then go ahead and get the H6, but, there's no reason to do so. The Outback is not a racing vehicle, rather, it's a great wagon and you'll be fine with the H4. Be sure to get the CVT, it's a superior transmission, you're always in the right gear and it is very responsive. There is no turbo option on the current Outback 2.5 and the gas mileage is great.