My mileage was different. With my old 2001 Subaru Outback, if I had the cross bars off, I was getting 28-29 on freeways. Put crossbars (Yakima round bars) on, and it dropped to the 24-25 range. Put something on crossbars (kayaks or bikes) and it really didn’t seem to change from what I found with cross bars on (maybe drop 1mpg). Never tried inflatable unicorn pool toy.
That’s why auto makers stopped commonly using cross bars and went to roof rails!
My experience pretty well lines up with yours. I don’t leave the racks on when not in use, but whether it’s a full size pick up or a small hatchback the drag makes a difference.
What I wonder about is the “aero bars” or whatever. I can’t believe they make a measurable difference.
Well I have a small car a Nissan Versa Note 2015. With no roof rack highway was 39 mpg ad roof rack thule Square bar and thule slipstrean and folded down j-bars and I dropped to 35 mpg. Add one kayak drop to 32 but even depends on which kayak. Ad Valley avocet drop to 32 ad Tiderace Pace Tour 17 or QCC700x only drop to 33 mpg. Gas mpg on lower speed limit roads like 35 to 45 MPH no real difference in gas mileage. Its highway speeds that effect my car most.
