I really appreciate the greater power of the 6-cyclinder engine on my 2011 Outback as compared to the standard 4-cylinder. And I have found that on the highway this engine doesn't give up much in the way of mpg. Keeping up a steady 75 mph or so, I get about 26 mpg pretty consistently for the tankful (I've got about 55,000 miles on the car). But I also own a 2012 Impreza, which is lighter and has the much smaller and less powerful 4 cylinder engine. Driving the same steady 75 mph gives me about 27 to 28 mpg, which for me is not very significant as compared to the OB. I do find that this little Impreza, if driven at a steady 55 mph, will go up to about 33 or 34 mpg, but where would you be driving that slowly on a highway? The bottom line for me is that the OB, that is far superior in every way to the Impreza, gets about the same mpg as the weaker, smaller, and more noisy Impreza. If I had to do it over, I would have not bought the Impreza even though it was about $10,000 cheaper, but would have gotten a second Outback. I have owned many, many cars in the 50+ years I have been driving, and I don't think I have ever had a car that I have been as satisfied with, overall, as my 2011 Outback. I used to think of myself as a VW man, then became a Honda man. Now I KNOW I am a Subaru guy!