Why am i not getting good MPG?

[soutthpaw]

I am sure Jack and others will jump in here too, but MPG reports are like fishing stories!!! (especially when the user's name is FishChris) So take it with a grain of salt. Tire rolling resistance will make a big difference. a highway tread Low rolling resistance tire could easily net +1 or more MPG's. Wind resistance is a big factor too. I'll see if I can find a graph to illustrate that and post it. Asphalt vs concrete highways will affect MPG too.

[th3godf4th3r]

well i did just change my tire size to 2541mm which it should be with 285/65/18 tires.

the programmer said it was at like 2742 or something

hmm i didnt know asphalt and concrete made a difference!

[soutthpaw]

Here is an in-depth article on MPG and tires. there are a couple of interesting diagrams on page 40 that show where energy losses occur in automobiles.. There is also reference to road surface effects on MPG
Tires and MPG

[88Racing]

Try using your custom tow tune.

But like Southpaw addresses there is a lot of different factors out there and they all add up for you or against you.

Take for instance:
Tire type.
Tire wieght.
Wheel weight.
Gearing.
Cai.
Exhaust.
Cats.
4x4.
Headers.
Trailing weight.
The list goes on.......

Lars

[soutthpaw]

Fuelly F150 MPG's

Is a good link to get more realistic MPG's

[JWBFX4]

Well just to put my 2 cents in here... The 33'" tires aren't helping the mpg (heavier tire and more rolling resistance) My first thought was you might haven't correct your speedo with the turner...but I see that you did. Wind also plays a factor. But two of the biggest things is 5600 lb truck vs hills equal bad gas mileage, and anytime you get over about 65 in these trucks throw the gas mileage out the window.

Here is a little data I gather about my truck on a 280 mile round trip. Most of this is interstate. I found that if I put cruise on 67 mph (65 according to the gps) I can get around 18.9 Droping down a little more will get me 19,4+
I also found if I put the cruise on at 77(gps=75 actual speed) I drop down to around 15.5-15.9 Sometimes a little lower but thats about the average. Now before I get slammed for anything I said the conditions was pretty much the same on winter blend fuel running canned level 2 3.73 rear end. Also mpg was being calculated by miles driven divided by gallon's of gas, not programmer.

But just to throw this out there if I run around 55 pulling the ole bass boat I can get around 17.5 then the mileage drops after that. But with the tire upgrade coming those figures will be off now

[th3godf4th3r]

ill trade ya fuel economy cory!

[Jackpine]

Southpaw and Lars pretty much covered it. I know Fishchris' truck, because he did a TON of postings in the "Appearance Products" forum in f150Online when he was getting his truck.

The boat he pulls is very lightweight, something less than 1000# with the trailer. His truck is an SCab, not an SCrew, so it's somewhat lighter than ours. It's 2WD, not 4WD like ours. It has 17" wheels. I don't know what his gearing is, but I suspect it's lower than 3.73.

So, everything I know about his truck tells me he SHOULD be getting better gas mileage than we do.

I averaged about 15.5 mpg in just under 1400 miles on our last trip at 70-75 mph (hand calculated at each fillup). I get around 12.5-12.7 when we pull our 3600# trailer. My tires are 275/65-18 Goodyear Wrangler Silent Armors and they have a fairly conservative tread - I'm sure mine have less rolling resistance than yours.

Both you and I have more bells and whistles in our trucks than Fish has. For instance, we have climate control, and it's ALWAYS on in my truck. That consumes energy.

I don't trust either the Gryphon's or the truck's MPG displays. The truck's is always lower than the Gryphon's average numbers and my "hand calculated" results fall between the two.

One point - unless your loaded tire circumference is correct, your speed and odometer values will both be wrong. For my tires, I've subtracted 3% from the unloaded tire circumference. Using Bill's calculator, that corresponds to a 7% rubber squish (since the wheel doesn't squish). I don't know what your unloaded circumference is, but you might try entering a value that is 3% lower for the tire size. (A larger number shows up as higher speed and more distance driven per tire revolution - and, when the Gryphon's speed readout is correct, the dashboard speed will be 2 mph faster, but the odometer will be accurate).

Finally, each truck is an "individual". Some will simply perform better than others and there's not a whole lot we can do about it.

Two more posts appeared as I was writing this "book". The "fuelly", site was quite interesting, Southpaw. Looks like the trucks getting about 15 mpg are in the majority. And JWBFX4's remark on the tires is dead on!

- Jack