Towing / Deck Plate Mod / MPGs (lengthy post)

Hey y'all. I just a 2169 mile trip from DC to Arkansas to southern Missouri back to DC. I was towing my 5' x 8' enclosed trailer, loaded while going to MO, empty coming back to DC. We took this route to Arkansas. http://goo.gl/maps/vsVRg
Once we were out of the back roads and on I-81 it was pretty easy going. With the truck/trailer loaded I averaged 15.5mpg with the Deck Plate Mod (DPM) on several tanks. Once we got to Nashville and stayed the night with a friend, I thought I'd put the DPM cover in to see if there would be a difference b/t Nashville and Little Rock. The road is fairly flat and open so I thought it would be a fair test. (We hit some nasty rain around Memphis) With the DPM cover in, my MPGs dropped to 13.32 and 13.00 over the next two tanks. Quite a difference.
From LR to MO, the route was all back roads through the mountains/hills of north AR (really, there are some mountains and hills out there and it is quite beautiful!) DPM cover off, still fully loaded my MPGs were 15.307. Overall loaded average was 14.711 MPGs.
(BTW, my wife was in my Camry and averaged 31.558 for the same trip. Highest tank was 34.726 and lowest was 27.836. Not sure why the significant difference. She had her, our two kiddos and some luggage)
Once we were empty, rested, and visited with family we hit the road. We took this route (http://goo.gl/maps/3xZbE) Getting out of the mountains/hills of that area hurt. Partially (well, mostly) b/c I was ready to get to the interstate, which was about 75-85 miles from our starting point, and I hammered down not caring about MPGs. That yielded a tank of 14.566. Still not 'bad'. Once on the highway I averaged 14.474 MPGs on the return trip (unloaded). A bit lower than the loaded weight but most likely b/c I was ready to get home. (We did our 1000 mile return trip in one day.)

Here's my truck/trailer, in (Dallas Cowboys Blue/Silver, as my wife/kids say)

 

well at first glance i would chalk one point up to the deckplate mod for giving you a couple extra MPG!

it may be due to the recalibrated ECU which has adjusted the fuel/air ratio to match the new air levels in the intake and when you put the cover back on it flips out and pumps more fuel in than is needed. not sure just speculating. i'm rockin my DPM open all day erry day and it serves me!

 

Fantastic information! Now I need to get around to doing/buying that mod. Anyone have the DPM for sale? lol.

 

Check out your local boat shop. Bass Pro, Gander Mountain, etc will carry them also.

I should have kept track of my speed better. When I make our trip to ND next month I'll try to take note better.

 

Your trip seems oddly familiar when my wife and and I moved from Kansas back to Washington. She drove her 99 Camry and I hauled a 6x10 trailer. I got an avg of about 14MPG while she was about 30MPG with the Camry. Highest was coming out of the mountains into Salt Lake City, she got 34MPG and I got like 19MPG. I had the deckplate open the whole time.