Took a 300-mile trip down I25 and back today. I've done this route four times before in similar driving and weather conditions. At altitudes from 5000 to 7800 feet, 3/4ths of the driving was on the interstate at 60 to 75 mph, 1/4th was in urban and shopping areas at 10 to 35 mph, temp in the 50s to low 60s, light wind from the left & right side, same gas station's premium grade, about the same load in the car. In the past, fuel economy was between 30.5 and 32 mpg as indicated by the OBC.
With the K & N filter in, fuel economy calculated by the OBC was just over 35 mpg.
I may submit this to Ripley's Believe It Or Not. I'm wondering what the numbers would be at sea level.......where there's more air.
I'm gonna do this again next week. I'll check to see if it's about the same numbers. Sure hope so.