Anyone's gas milage increase with trailer...like big time...?

[Moneyslinger]

My everyday non-towing gas milage in my 2012 Toyota 4WD Tundra with 5.7 engine is around 14.5 according to the built in gauge.

And then we bought our first trailer just a few weeks ago.

Soooo...before I left home to pic up our 7400lbs trailer in WI and tow it back to IL – that's about a 2+ hour drive – I reset my gauge before the drive up to make sure my normal 14.5 to 15 mpg was "true".

Once there I got all hooked up ready to leave and resent my gauge for the trip down, fully expecting about 9 mpg from what I've been reading, but to my surprise my gauge was reading between 26 mpg and 28.5 mpg.

Yes, 26 mpg and 28.5 mpg. Something must be wrong, right?

In total the trip up and down took a bit less then a 1/2 tank...that in total is about a 4.5 hour drive, with a 7400 lb trailer for half that drive. That's not too bad at all...right?

Soooo...once home I parked the trailer and continued driving normally for the rest of the week, until it was time fill up. I took a look at the gauge before fill up, that as now reading about 22, which would seem right on average if I drove off the other half of the tank without a trailer.

I filled the tank and reset the gauge, to find I'm getting my normal 14-15 mpg again, that means the gauge is working fine.

So a few theories:

1. We were heading "south" on the way back with the trailer - and that's downhill...???

2. My trailer was so heavy, that my front wheels where barely touching the ground, and my gauge gets it's reading from front wheel tire rotation....???

3. Northern winds push me along? But this was mostly back roads driving for the most part, through small towns...with some hi speed 60-65 mph driving as we got on route 12 near the border.

That's the best I can come up with.

Anyone want to take a stab at this?