Any improvement in fuel efficiency?
I wish I knew...
I put new, different spark plugs and the K&N air filter in at the same time, plus different tires than the last trip to this destination.
This super hot desert/high elevation mountain trip two years ago was with 2 people, we had 3 people this time so a lot more weight in the car. Last trip I got about 37.5 mpg, this trip we got 40.9 mpg with A/C on 95%.
The car drove great and was quieter, this is an early build 2013 Job 1 FFH with 18" wheels/tires. You have a 2015 FFE with all the new improvements so I don't know if this air filter would be worth the effort.