Buck50HD

I wouldn't be too sure that a 12' 5th has less drag than a 10' TT but it would be interesting to perform a physical test or run some CFD to investigate a little further. The 12' rig is displacing more air but might be more efficient.

My intent was just to point out that although you have unusually high mileage, you also have a modded diesel and one of the lowest profile TT's on the market. Not to mention that the OP is probably looking for comparable gas 1/2 ton rigs.

Mechanik

As the OP, I thought I'd chime in and thank everyone for their posts. The email associated with my account seems to have died, so I haven't been getting the updates lately.

I was originally looking to validate my experienced mileage, which seemed a little low. Based on the feedback, though, I suspect my original mileage was fairly average, given the truck, camper, wind, and (excessive) speed. I have a new appreciation that 70 MPH, uphill, in 30-60 MPH headwinds with a high-profile 5,000 lb. camper results in poor MPG.

What has been very cool, though, is looking at the descriptions of the trucks, weights, trailer profiles, and speeds. Things I hadn't really considered in my original post. Like many people, I'm always wondering what my next truck and camper will be and this is really good info. At this point, I'm jealous of you ECO and diesel owners!

Can't wait until the F150 Hybrid comes out with a 10k towing capacity and 50 MPG! BTW, recently installed an Edge programmer and can't wait to try it out towing. Three tanks of gas show a mixed driving mileage increase from 14.3 to 16.2. Unfortunately, even freeway driving involves a lot of stop and go in LA LA Land.

idivemike

Over the last two days I went from San Diego to Houston. I had about 1300 in the truck and was towing about 4000. In my 2005 5.4, stock tires/wheels I ended up with 12.0 mpg. I was up around 12.4 and climbing the first day but the second day became more about getting there than driving smooth and easy.
Wanna save gas, draft an 18 wheeler!

Buck50HD

Was the frontal area over 80 square feet?

idivemike

I doubt it. What is the frontal area of an f150? Throw in a few more sg ft that my trailer stuck up above the camper shell, say 6 sq/ft for 1' high and 6' across, and there you go.

Average speed was probably 70.

Mechanik

For those discussing drag coefficient (Cd) and frontal area, how do you measure these? I find internet data on Cd for naked trucks (without mirrors, BTW), and usually for short beds. Same with frontal area, which seems to be "effective" frontal area as modified by aerodynamics. Unfortunately nothing on how to calculate frontal area and Cd. My limited algebra skills tell me this could be a terrifically complex calculation.

On the simple side, do we just assume all our trucks are the same, so the difference between mileage is the trailer frontal area? Not a bad assumption, but it seems to me that this is good for SWAGs.

I recently compared my Info Center mileage, Edge mileage, and gas-station fill-up mileage on a full tank of 70% freeway driving. Info says 16.7 MPG, Edge says 18, and good 'ol math says 18.99. Suddenly a 2 MPG delta on similar rig/config sounds reasonable.

brulaz

AFAIK calculating DC would be impossible. Too much going on. You really have to measure it in a wind tunnel.

And all trucks are not the same. Tires, wheel size, lift or not, bed cap all have an impact, especially at higher speeds where drag is important.

I've compared my calculated mileage with the Info centre for every tank. Their averages are essentially identical (within 0.03%). In any given tankful, I imagine the error is in how close I am to actually filling the tank, not the info centre.

The biggest differences I see on mileage is winter vs summer, wind speed/direction (towing esp.) and of course speed and traffic (stop and go, idling, is the worst). Anything over 60 mph also hurts, especially with a trailer.

idivemike

I have a strong suspicion that driving under 60 on the interstate will eventually hurt a lot more. That sounds dangerous!

All other stuff aside. In the last week I drove my 05 f150, stock, with a trailer from San Diego to Houston and then to Illinois. Drafting works! I watched the computer on the dash (lariat feature) and my gryphon tuner set for immediate average and over all average. All three reflect the benefits of drafting to be over 1.5 mpg.

stx03

^
Talk about driving under 60mph being dangerous

Recommends drafting

brulaz

Looking at your vehicle stable, think I understand where you are coming from.

But I do hold my speed at 60mph (maybe a bit more - 100km/h) on the interstates and as long as there's a passing lane, there's been no problem.

What's dangerous is some of the other nuts on the road. A few years ago I was doing the speed limit (90km/h) on a 2 lane in Ontario, when a trucker decided to pass me on a hill in a no passing zone. A car came over the hill and was run off the road. We weren't run off although it was close. Often thought it was a stolen load ...