Disclaimer:
Do not try this at home. Nothing "unsafe" was done in this test, unless you consider 10-15 mph over unsafe. No wreckless acts were performed and no innoncent persons lives or properties were put at risk. Driver and personal safety always took precedence over any objective throughout this test. All objectives were performed when safety permitted.

Hypothesis:
Keeping engine RPM under 2,000 RPM, using slower acceleration, and increasing tire pressure will result in improved fuel mileage.

The vehicle:
2007 Ford F150 FX4
5.4L 3-Valve V8
300 hp, 365 lb-ft torque
3.73 Limited Slip rear axle

Week 1:
For the first week of testing, the vehicle will be driven with a heavy foot. From each stoplight or on-ramp, acceleration will be maximum and top speed will be 5-10 mph over the posted speed limit, or 75-80 mph on the highway (depending on the normal flow of traffic on a given day). When a slow down is needed, as soon as the vehicle gets out of the way, the gas pedal will be floored causing 4-2 downshifts and max RPM while regaining speed as quickly as possible. Stop signs will be stopped at fully and maximum acceleration will be performed from each stop, as traffic will allow. On the highway, RPM's were around 2300 when cruising, and often hit 3-4k when accelerating. 90% of driving was highway. Tire pressure was set to 32 psi.

Week 1 Results:
Miles driven: 220
Gasoline consumed: 15.3 gallons
Mile per gallon: 14.4

Week 2:
For the second week of testing, the vehicle will be driven as slow as possible. From each stoplight, the gas pedal will be pushed down just enough to allow acceleration without going above 2,000 RPM's. At on-ramps, a stead speed will be used throughout to as slowly and safely as possible merge with traffic, without allowing the RPM's to reach above 2,000. Speed will never exceed the posted speed limit, except on downhill sections where the extra speed can be used to help gain momentum up a coming hill. Stop signs will be slowly rolled through, when safely possible, at 2-3 mph, and the gas pedal slowly applied to allow a slow, steady acceleration. On the highway, RPM's were a steady, constant 1,800 and very little shifting took place. 90% of driving was highway. Tire pressure was set to 38 psi.

Week 2 Results:
Miles driven: 282
Gasoline consumed: 20.1 gallons
Mile per gallon: 14.1

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Results:
Gas mileage did NOT increase, and there wasn't enough of a decrease to call it a decrease. I'd say it remained constant. The variables were quite extreme I can assure you. During week 1, my truck often smelled when I got home...I definitely drove it hard.

I can say it was a much more calming experience during week 2 though. I definitely used much less brakes that week.

I have no idea why my gas mileage didn't increase. Common sense would tell you that it would. I used less brakes because I wasn't constantly speeding up and slowing down...and if you go from point A to point B twice, the first time you hit the brakes a lot, and have to use more power to overcome those brakes, you should use more fuel. But for some reason, that wasn't the case with this test.

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My regular driving style is to pretty much accelerate as fast as safely possible and then level off around 5-10 over the speed limit. On the highway, I pretty much get in the fast lane and follow the safe flow of traffic.

 

This is a joke, ... right?

If not, then you have a serious issue with your drive train. Most everyone here with a fairly stock truck can EASILY attain MUCH better MPG that what you have posted.

I average approximately 15-16mpg combined. I have seen 21mpg on open interstate driving @65mph. So you live happily with your claimed 14mpg and I'll live with my 16-21mpg.

 

Interesting, but there are so many variables that effect gas mileage that tests like this are pretty much worthless.

 

I find the data interesting, however very different from what I am experiancing with my truck of same year.

 

How many miles are on your truck? Is your engine even broken in yet?

 

My 2005 4x4 only gets average of 14.5 city driving. I get 17-18 on the hwy. I never and I mean never do wot open runs on my day to day driving usually 1/4 throttle. I have tried the never go above 2000 rpm deal with no results. I usually drive with enought acceleration that the shifts happen around 2200-2600 rpms. Just looked at my window sticker and it says 14city / 18 hwy so I'm pretty much in that range. My brother that drives the equivalent truck except its a Chevy laughs at me cause he consistantly pulls 21-22mpg with mixed city/hwy. oh well

 

i have the same exact truck as you, an 05 4x4 scab. yet i am only getting 12.7 city, and 13 highway. i dont have a lead foot, i drive very conservatively. all i have on my truck is a 2.5" level, and 325/60/18 nittos. could those tires really be pulling my gas mileage down that much? oh yea i also only have 17k miles on my truck if that matters.

 

That's the problem. With most of the miles driven being on the highway, it does not make that much difference in fuel mileage to go from 65 mph to 75.

And, the test needs to be done with at least 3 tanks of fuel for each. To many varibles to just do it with one tank.

You would need to fill up at the same station, same pump at the same time each day. Temperature makes a big difference in the amount of fuel you actually pump. The cooler the temp, the denser the fuel. Fill up on a hot afternoon and you will not get as much fuel in the tank.

Slow fillup vs fast fill. Have to fill slow to allow air to escape.

Idle time. Hit the drive through for coffee a couple of times and it will hurt fuel mileage as much as a fast acceleration.

Just having to use the defroster more, can have an effect. Same as running the a/c.

Something is not right for sure. I think alot of us have proven easily how much you can adjust your fuel mileage by the way you drive. So there has to be something effecting your results.

 

For all you folks that constantly drive conservatively with the tach rarely touching anything over 2000 rpm, I have a test for you. I drove conservatively for quite some time. The other day I decided to open it up WOT. Wow, quite a bit of smoke came out the back I tells ya! What a build up of carbon, and who knows what else. Now I'm back to my normal driving style. I've WOT'd it a few times since and no more smoke shows.

So, from what I've heard, especially with VVT engines, it's actually better for the engine to be driven hard every now and again. For those of you that have been babying your truck, WOT her once and angle your passenger side mirror towards your tail pipe and watch.

I think I stepped my gas mileage up a step or two from hammering the throttle, so there's probably some truth in the OP's post.

 

I never need to go beyond 2,000 rpms in my V6. It's awesome.

 

Actually, it MAKES A HUGE difference. The difference between 60mph and 70mph in a full size truck is substantial! The frontal area of a truck is about as aerodynamic as a barn. The applied drag which results from this frontal area increases exponentially for every 1MPH increase, it's not a linear scale my friend.

Google, Yahoo, Ask Jeeve's it, or enroll in Aeronautical Engineering degree.

 

well, it is hilly around here in Pittsburgh, even the highways. So driving easy vs. fast is probably not going to make a difference in moving these heavy trucks up the hills. But still, for 90% highway driving, your MPG avg is low. I rarely drive highway around here but say if I go up I-79 to my camp, I get 16 to 17mpg. And that is just one tank difference vs. my regular local driving avg of 12-13mpg. So you don't have to run multiple tanks to see a difference.

My best highway Mpg was driving to the beach in NC and SC where it's flat I got 18/19mpg.

 

i don't know how this plays into the whole thing, but my mileage has dropped noticeably this week. the only change i made was putting in 89 instead of 87 at the pump last week.

 

I have a 05 4x2 with the 5.4 and 3.55 gear I get from just under 12mpg to about 14 most of my driving is city with a lead foot. On long highway trips with cruise set from 73 to 78 depending on traffic flow I get 18 highway.

 

I've got a bone stock 2007 FX4 and get better MPG than that (14.5 City / 19 HWY). But, I'm also running 20 inch Pirelli's at 44 PSI.

I had no problem keeping my 2005 FX4 (and older F-150's) below 2000 RPM while accelerating. My 2007 jumps right up to 2200 RPM no matter how light I am on the pedal, and I'm at 2200-2300 RPM at 60 MPH. MPG is much better at 55 MPH than at 75 MPH, though it doesn't seem to get any worse from 75 MPH to 100 MPH.

Brand of gas doesn't seem to make much difference, but gas station does. I lose as much as 2 MPG using the BP by my work vs the BP by my house. And, 87 octane seems to be better than 89. A 50/50 mix of 87 & 89 performs the best.