The answer depends on several factors, such as tow vehicle, topography and weather conditions. All I can offer is talking about my experience. I live less than 40 feet above sea level near the Central California coast. I can’t go anywhere, other than some local beach campgrounds, without traversing steep grades and mountain passes that really suck down the gas, especially in a challenged tow vehicle.  Also, tend to encounter relentless headwinds traversing the high desert regions. To put that in perspective, I lose about 10 mpg, sometimes more, towing my Rangerunner with a 2.0L Subaru Crosstrek and about 1–2 mpg towing with a 4.0L Toyota Tacoma. The Tacoma never struggles as the Crosstrek often does. I’ve never been to Florida but a quick glance at a relief map of the US leads me to believe that someone who lives along the coast in that state would have differing towing experiences and MPG’s with identical vehicles than I do. 

I towed my CoolCamp from SE Mich to Natchez with my Mustang, 2.3L EcoBoost — not the ideal combination for towing but that’s me.

With a STRONG headwind of 30-ish MPH I went from 27 car only mpg to 17 at no more than 70 MPH.

On the flats of Miss. 19 to 22 mpg at 55 MPH.

bob

I drive a FJ and lose between 7 — 10 mpg towing a V model.

We bought the range runner in Summerfield, FL. Nov 21, 2022. We put 1500 miles on since then. Our 2010 Dodge Grand Caravan has been getting 24 MPG driving 60mph to 65mph. The range runner has a 4′ x 6′ frontal area, and with the tires and axle, say it has 26 SF frontal area. The lowest average fuel economy with the trailer was 17.5 mpg and the highest was 20 mpg. I tested averages at 55, 60, 65, and 70. The lowest average was likely caused by fuel bought at a Shell station where the gas must have had over 10% ethanol added. I reset the average economy at the fill-up and saw immediate 2 mpg drop. Nothing else changed. 70mph also caused 1.5 mpg drop. Not sure about tire pressure, but the factory inflated them. The total equipment we were carrying in the car and trailer not including the trailer weight I estimate at no more than 500 lbs.

just got my RR.  I have a four runner and didnt see a drop.  But mine 4R roof line is higher than the RR.  I read somewhere that was an issue with shorter vechicles