I don't have numbers but I know my MPG takes a dive. Since my overhead is still accurate (stock) I habitually leave it on... & see an immediate loss in the AVE MPG. I have heard similar comments from others. In my case, the trailer is a simple 16' single axle landscaper's trailer. No brakes. It does have the expanded metal mesh ramps. It I'm running empty, I can & have laid the ramps forward flat on the deck with a tiedown, though never checked MPG like that.

I'm not hauling hay anymore but this is the only pict I have available. It does give a good idea of the trailer & the amount of nose high angle.

I do notice the the trailer is still a bit "nose high" despite the 4" drop on the hitch insert. I had the insert & it works. I wonder if the trailer is catching air underneath the way a lifted truck does...

I have regreased & adjusted the wheel bearings but was unremarkable.

I find it hard to believe that such a nothing trailer has a significant impact on MPGs.

All the trailers I've towed around even my 8x8 has a huge impact...Then my Jayco...My 8x8 tend to drop me around 14-16 MPGs relm. Then my Jayco for the 2 trips I've done so far have drop me to 9-11 MPGs...

That mesh ramp may as well be solid at speed. So much turbulence that air really can't pass through it. I don't notice any change in mileage once I hitch up regardless of load. Empty 4500 or with 12k on the deck has less than a 1mpg impact. With such a light trailer in your case it HAS to be that big ramp though. You're probably only towing 1000#, but it's a big wall too.

My road trip last year with the Toy Hauler... was in the 9-10 range. I don't like that mpg but I understand the truck was working, hauling that billboard at highway speed! (~60 all highway, Mass Pike & NY Thruway). It just seems like a big hit for the light trailer. Running empty, I'm normally in the high 16's to 18's on happy occasions. I'd like to understand & hopefully improve the mpg differences. Like how much is friction... how much is windage??? Anybody have experience with these? AirTabs http://www.airtab.com/main.html If they worked, wouldn't over the road truckers all be using them?

2nd gens must have more accurate OH's that 3rd gens, mine is off by about 15% stock. I tow a similar trailer once a year just over 525 miles round trip. There is a lot of elevation and about 100 miles of dirt road in the trip. The trailer has 24-26 bales on in going in, and is empty coming out. I generally get about 14 going in and 15.5 coming back. The same trip without a trailer, but a bed full of hunting gear, gets me 16-17.

Maybe I've just been lucky but every time I hand figured MPG, it agreed with the overhead. At 55K miles, I still have the OEM rubber on it & I've not got the XZT+ installed yet... so that may change. If it does, and I expect that it will, I'll miss it. On a trip, I can right foot better than the cruise & a readout confirms how I'm doing.I am considering getting a hitch insert with more drop... Wondering if leveling the trailer would cut the drag.

Russ, you may find that your trailer will pull a little better when it is level, but your mileage won't change much. The largest factor for towing economy is the wind resistance. I have had two different fiver trailers and the taller they are the less mileage I get. They both weighed about the same too.