Im gonna start a list of things I think effect fuel economy of a vehicle pulling a trailer
Speed of vehicle
Wind- direction and speed
Aerodynamics of vehicles
Grade-Uphill or downhill
Tow vehicle tires- air pressure, tread type, size, rolling resistance, stability
Trailer tires- air pressure, tread type, size, rolling resistance, stability
Weather-dry,wet roads, rain, snow
Time of day- sunlite, night
Engine- oil, air flow
Driver- Throttle use, acelerating, deacelerating
Hitch- stability, solidness
Weight- on each axel
Right foot, speed, and wind direction/speed are the three biggest factors in fuel economy when moving a large object down the road. Oil type can make a difference too (dino vs synthetic). I found my sweet spot on the highway pulling the 5ver with the F250 6.0 is around 62-64 mph. Higher and fuel mileage dropped off. Going slower didn't hurt, but didn't help much either. Battling a headwind could scrub off 2-3 mpg off the 11 I was getting while pulling. Being smooth with the right foot can make a significant difference.
2011 Ford F-150 Lariat Crew Cab 4x4 EcoBoost
2014 Cruiser RV Fun Finder 215WKS
2012 Harley Street Glide -ember red sunglo
Yamaha Grizzly 660 (his)
Polaris Sportsman 500 H.O.(hers)
I'd say pre purchase, you control vehicle selection; gears, engine, other truck specs, height and weight.
After purchase, its all in the right foot. Also route selection may help (less hills vs mountains, lower speed side roads vs interstate).
In the end, speed at 50mph (80km/h) would probably net the best mileage on most rigs. Also net the most road rage from other drivers.
Until manufacturers change how our trucks are engineered, we are stuck with what they offer.
Speed is the main thing you have control over. I've never seen MUCH difference in mileage between mountain driving and driving on the plains. Yes you get less mileage going up but much BETTER mileage going back down and USUALLY you eventually end up at the same elevation you started from. Many of the others on your list would be next to impossible, even under laboratory conditions, to measure any difference.
2011 F-150 HD Ecoboost 3.5 V6. 2550 payload, 17,100 GCVWR - 2004 F-150 HD (Traded after 80,000 towing miles) 2007 Rockwood 8314SS 34' travel trailer
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