itsafarm truck

Made a trip last August pulling my 6400 lb camper and got 10 mpg. Made the same trip yesterday and got 7mpg. Same road, same camper, same truck, same speed, and exact same campground. Not sure what would make such a big difference, no codes and truck didn't "feel" any different.

schmenke

Wind? Barometric pressure (assuming you have a normally aspirated engine)? Tire pressures?

l3rian

Wind conditions, fuel type/ brand, maybe a brake is sticking on the trailer? Traffic. Lots of variables, but that's a 30% difference. I'd start with the trailer brakes. Check to see if they're hot after you tow.

mass-hole

I was going to say wind. I usually get around 10mpg but then I went down to St George last trip and experienced the same thing. 7 mpg. I was going into a constant headwind.

BlackBoost

Other than wind and temperature, it's also possible that your load on that trip might have caused a bit of sway. This causes the truck to apply brakes to specific wheels and to the trailer to stop any swaying. This will of course affect your mileage. I always turn sway control off unless it's a very windy day.

Another cause could be the engine. About a month ago I noticed my mileage get worse for no reason. Same drive to work every day, same route that I've been taking since I got the truck. After a while I got a check engine light for a failed crankcase pressure sensor. Replaced it and my good mileage came back.

acdii

More than likely you had a head wind more than last time, or a tail wind last time. Wind is the largest factor when towing and has a huge impact when driving into it. Even a offset wind can cut into fuel economy enough to be seen.

Ryan_2020

I just did a 400 km round trip (over two days for work).....got over 1 mpg less on the way home just from the wind (noticeable head wind).....unloaded.

Wind could easily drop you 3 mpg towing.

BlackBoost

Yep. On a nice day I can get 12.5 MPG towing my TT, 13+ with a tail wind. Last Saturday driving in a wind storm I got 9.5. It was an... interesting drive...

StonedFX4

I was cruising on the interstate at 68 or so into a 20 mph headwind, no TT, just the truck with 2 people and luggage, watched the mpg drop as the day went on. Was a bit surprised at that, but that's life. Went from about 22 down to 17.5 mpg in just a few hours fighting the wind.

acdii

I see this happen all the time, I could have a good start to the tank, seeing 21, then have a windy day and it drops to 18.