Here's my "latest" fuel test so far using ScanGauge with a 2003 Tacoma 2WD 2.4L 5 speed manual transmission & Leer Shell:
Getting 32 to 33MPG when averaging between 50 to 55MPH on back roads. Gets 29MPG @ 65MPH on interstate.
When towing high profile CampLite Camper in non-mountain areas with Kayaks on shell & bicycles between pickup & camper (about 2000lb load), gets 16MPG @ 60MPH on the interstate, 17MPG @ 55MPH on the interstate, and 18MPG @ 51MPH on backroads. Best fuel economy so far 19.5 MPG between 45 to 50MPH on back roads. Worst fuel economy so far 55MPH @ 15MPG on the interstate with headwind.
Found (by accident) fuel economy & towing power slightly better with lower camper using 2" drop hitch compared to 3/4" lift hitch towing camper, "guessing" due to better aerodynamics when towing high profile camper.
Towing 1900 to 2000lb low profile boat gets 20MPG @ 65MPH on the interstates.
We like the Leer Shell because it allows for storage the animals can't get to at night while camping and the Thule rail/rack system for hauling Kayaks.
Rig with 3/4" lift hitch:
Rig with 2" drop hitch: