hard towing with Honda Pilot - HELP

A great example.  I recently drove to Ontario Canada and back, but only with a motorcycle on a hitch carrier (300 pounds max).  It was 428 miles each way. But I noticed that from central Connecticut, it was FLAT driving, with almost no grades whatsoever through NY and Canada. My fuel economy was 32 MPG vehicle indicated, and 31.5 MPG actual calculated. 

I have NEVER gotten that kind of mileage on highway from Connecticut to Vermont. Ever. Maybe 28 MPG best, with a mountain bike on the back hitch. Hills make a huge difference, and head winds are just as brutal. 

 Were you in the next lowest transmission gear (if a 6 speed, use 5th, never 6th). Allow the engine to make more power by running higher engine RPM's. If your transmission hunts 5th-6th, don't let it. Constant gear hunting will also cause worse fuel economy and more transmission heat too.

 Is your Pilot brake system in good shape? Have you check pad thickness to see if you have  stick caliper piston? Does it pull when braking? The tow vehicle is just as important as the trailer. 

If you hitch your R-Pod to your Honda Pilot, then use an auto jack to raise one R-Pod tire of the ground, and see if it spins free with no bad play or grinding noises. Being hitched makes for safer jacking of the trailer.

Ethanol free would give a higher mpg than gas with ethanol because ethanol has less BTUs per gallon than gasoline. See this Gasoline gallon-equivalent article for details. It also helps explain why Diesel engines get better mileage.

We just finished a trip of about 6,500 miles. I had greased the hubs before we left. I don't know what you mean by "a long time." If the grease is still good, it would be okay. As stated by Keith-N-Dar above, you would have felt heat and likely not completed the trip. The brakes dragging could be a factor if they are too tight and causing drag or if the pin had been pulled and they were having to overcome full-on brakes. If that were the case, I think you would get less than 9 mpg.

What speed were you driving? Anything above 55-60 mpg and you are looking at a very significant mileage hit due to wind resistance. Wind resistance is not linear, meaning that it does not increase proportional to the speed, but exponential, meaning it increases much more than the speed. There is an article on RV.Net that you should look at to help understand this.

We just goy back from a 500 mile trip and before we left I accidentally filled the truck with high octane fuel. My truck went from around 12 MPG to nearly 15 MPG.  I need to test it because once in a row isn't a trend but the higher octane suggestion may be a good one.  In this case the gas was also ethanol free instead of the normal 10 percent.

If it is your wheel bearings causing drag they are shot now.  Your hubs would have been hot and most likely you wouldn't have gone far.  Jack up a wheel and spin the tire listening for noise in the hub.

Good luck and let us know what you find.

On our Frontier, I find that if I am in mountains or hills, turning overdrive (OD) off helps. I leave the transmission in Drive otherwise unless I am on a 6% or more downward slope. On this trip so far, mileage has varied between 10.6 and 14 (one exception of 17) mpg per tank. The low ones had lots of climbing and/or headwinds. The high ones were aided by a tail wind and/or more generally downhill. So far, we have been from near sea level to about 8,000 ft in elevation.

Also, I noticed that gas octane ratings out west were different.. Instead of regular being 87 octane, I have seen 86 and 85 octane. Since the Frontier specifies 87 octane, I have been using mid-grade which has been 89 or with the last one, 87 octane. Performance has been better. I should try premium when we fill up next to see if that also makes a difference.