13mpg-help!!

Discussion in 'Start Your Journey Here' started by endura, Sep 11, 2007.

  1. endura

    endura Member

    Don't jump on me, I need this vehicle for my business.

    2004 Ford F150 with heavy duty payload package. 4.10gears/5.4L engine/4X2

    I drive conservatively, rarely exceed 62.5mph on highways and coast and anticipate lights/traffic. My truck is rated at 13/17 but I think that's with a regular cab and the lowest gear ratio. my truck is a supercab(800lbs.+) and has 4.1 gears as opposed to 3.31 gears. I also carry a consistent 500lbs in the bed with spikes of an additional 500lbs once a week.

    regular driving gets 13mpg. I tried a fuel economy run which is my regular 50/50 city highway driving route but with a 100% commitment to maximizing my fuel economy and got a whopping 15.5mpg. I have to admit though, it was a painful experience.

    my question is, concerning gearing. how much of a mileage gain will I achieve if I change the rear end gearing on my truck to the 3.31 ratio. I calculated a drop at 62.5mph from 1950 rpm to 1600 rpm. will this make a difference in real world driving or is it just maybe 1mpg, which really is not worth it on a cost/payback basis.

    thanks in advance for any and all suggestions and, no, I actually do need this truck for work and yes, I would rather be driving my old crx.
     
  2. BailOut

    BailOut My favorite holiday is Earth Day!

    Welcome, endura. Unfortunately, with a setup like yours single-digit gains will be all you'll likely see. However, rather than looking at it like only getting from 13 to 15.5 MPG, realize that this is a whopping 20% gain! You're in the mileage realm of RVs and Hummers so every little gain is going to be a big percentage.

    As you guessed, I also estimate that switching the gearing would grant about 1, possibly 1.5 MPG. That might not sound like much but that would be a 10% gain! Most of us would jump at the chance to gain an additional 10% FE boost with a bolt-on mod. heh

    Also be sure to pump your tires up to max sidewall pressure, or as near it as you can stand. That will help, especially with all the extra weight you carry.
     
  3. 2TonJellyBean

    2TonJellyBean Well-Known Member

    Pump up the tires to max, use a ScanGauge and lots of coasting and drop your speed from 100kph to 85kph for starters... and a numerically lower axle ratio would be a big aid at any speed above 65 to 70 kph because a 4.11:1 rear axle is pretty tough on mileage.
     
  4. ILAveo

    ILAveo Well-Known Member

    The payloads you described don't require anything heavy duty, so you might consider getting a plain vanilla six cylinder big cab F-150 manual transmission (or maybe Ranger if size isn't a concern) for your loads. Otherwise look at your truck and see if there is a bunch of un-aerodynamic equipment like ladder racks on it that you don't really need.

    The 6 cyl automatic F150 X-cab with topper, supplies and tools that I drive sometimes at work is only in the upper teens to about twenty at best, so I'm thinking you should set your goal with your current truck somewhere in the upper teens (ouch!).

    Most people improve their mileage by taking a lot of baby steps. The guys above offered some good advice. Read the articles elsewhere on this site for a bunch more good suggestions. The best tool I've come across to see if my steps are in the right direction is the scan gauge that plugs into the diagnostic port under the dash and provides feedback about instantaneous and average gas mileage.

    Welcome and good luck!
     
  5. warthog1984

    warthog1984 Well-Known Member

    Changing the axle might help. Not sure why your mpg is so low. I drive a Dakota 5.2 (14/18) and the lowest road mpg I've ever gotten is 14 even hauling 800lb of rebar. Do you have a bunch of stop-and-go downtown city traffic? Is this off-road mileage? Is your tranny in good shape- full, ATF not burned, not slipping, etc... ? Do you have a hung brake (maybe from a trailer hitch)?

    As for the axle, it looks like it'd be a 15-20% gain depending on operating condition.
     
  6. msirach

    msirach Well-Known Member

    I posted this 7-27-07.

    F150 EC FX4 hypermiling
    I borrowed a friend's shop truck today to pick up new bedroom furniture for my daughter's room. My wife still hasn't got off of her shopping "high" after Hybridfest.

    It is a 2004 F150 4x4 FX4 extended cab with a 4 speed auto, and 4.6 V8.
    I drove it 32 miles with the scangauge each way. Driving speed was 50mph.

    Trip there: 23 mpg
    return trip with over 500 lbs in the bed and sticking up about a foot above the cab: 22mpg

    EPA: 13 City, 17 Highway, 14 combined

    164% over combined there

    ONLY 157% over combined loaded.

    I checked the tire pressure before I took the truck back to him

    Right front tire was 41.5 psi the rest were at 38psi.

    Without the Scangauge, it would not have been possible to get as much MPG .

    Diamond Larry, you're right! TP is critical. 1 point TP is even more important on that hog.




    Throttle control/speed is a major factor and the rear end gearing in your truck makes speed even more of a factor. I used the Scangauge to watch throttle pressure and drove with rock steady throttle control. The truck is used by my friends company for mostly local errands and they get in the 10 to 11 mpg per tank range. For this trip, I ran at 50 mph max.
     
  7. lightfoot

    lightfoot Reformed speeder

    If your loads will permit it, a bed cover might help. Or better yet a lightweight cab-high cap.
    And I agree with all of the above, particularly dropping the speed.
     
  8. endura

    endura Member

    I need a four door truck because I drop off 3 children at school in the morning.

    Also, I needed an 8foot bed and the only combination of the two was this particular truck. About once a month, I actually load over 2000lbs into this truck, so the payload capacity is being used, albeit not everyday.

    The tires are at 60psi already because that's what the heavy duty package calls for.

    I have a folding tonneau cover already as I organized all my tools supplies to stay withing bed height.

    I used to have a 2000 nissan frontier 4 door pickup V6/auto with a camper top and a roof rack as everything didn't fit in the bed. with that combination, same general driving routine, I was getting 15mpg. Before that, when I first started, I had a 4cyl. 5 speed 1991 mazda mpv minivan that averaged 17mpg, but, freeway merging came to the point of being dangerous.

    I already posed my question on some applicable truck forums but people there, not all, seem more concerned with adding gigantic tires than maximizing efficiency out of their vehicles. which is fine, that's the point of a free society.

    I've scoured the net for anyone that actually did a gearing change on a truck (or any other aerodynamically challenged vehicle) and kept track of the fuel usage, couldn't find any. The best example I see of a fuel efficiency tuned truck is the GM full size hybrid pickups and those are showing 20mpg highway.

    the truck is tuned, runs perfect, synthetics everywhere. The only reasonable mechanica change I can see is a gearing change but it's just not worth it for 1-1.5mpg gain, and that's probably highway only.

    Also, is optimal fuel economy the lowest rpm at top gear with TQ consistently locked, regardless of throttle pressure. Is that correct?

    Sorry for the rant and thanks for the advice.
     
    Last edited: Sep 11, 2007
  9. Chuck

    Chuck just the messenger

    Aero mods can help a lot.

    It's strange, but there is actually more drag if the gate is down. ???

    Covering the bed when empty is the best thing on streamlining.
     
  10. endura

    endura Member

    I read that with an 8 foot bed, it's actually better to have the gate down. but, I'm carrying loads and don't have that option available.
     
  11. johnf514

    johnf514 Zoom? Try Glide!

    With all due respect, I think this is a silly reason to have a four door. Unless your kids are of high school age, there is no reason they can't sit in the back of a two-door for a ride to/from school.

    I did a little research on the F-150, and it looks like the 8-ft. bed isn't an option with the V6. With 2000lbs of weight, the V6 would do alright. How about a smaller truck with a bed extender?

    When not towing, keep your RPMs as low as possible. I'm assuming you're in an automatic, so gently roll on the throttle and keep your revs under 1500. Cruise in your highest gear and lowest RPM. Predict traffic/stoplight changes and coast up to them in neutral with the engine switched off. Do not idle at lights more than 20 seconds. Limit highway speeds to 60 MPH and on-ramp RPMs to 2500 RPMs.

    It sounds a bit drastic, but if you want 50% gains, you're going to have to work for it in that beast. Lots of engine-off time, lots of coasting, and lots of very slow starts. :)
     
  12. Shiba3420

    Shiba3420 Well-Known Member

    And you can artifically increase your gear length. Try starting off in second gear & shifting up to the next gear just before the current gear feals comfortable. However, if you end up compensating for the difference in gears by giving more gas, it may hurt your economy.

    As far as covers go, this is true and false. Go to discovery & look up myth busters or try to watch the show and it will explain the details, but it looks like the following things come into play...
    Assuming the bed is empty & tailgate is up;
    1. Just behind the cab, a vortex will form, like a tornado on its side. When the truck was designed, it had those in mind and adding a cover will change that vortex, usually making it smaller. That may help slighly in economy, but isn't very noticable.
    2. behind the vortex, in the remainder of the bed will be dead space where air doesn't move very much. Since it isn't interacting with the air passing over the truck it doesn't represent much drag, and covering it with a cover won't help.

    With the bed empty, and the gate down;
    1. remains mostly the same, but the vortex is someone unstable, and everytime is changes size, speed, shape, additional drag will be created;
    2. the air that was stable & unmoving can now flow out the back, and it does. This also creates interaction with the air moving around the truck & increases turbulance & drag;
    1&2 combine to DECREASE full economy, however a #3 may be added to the equations
    3. If the gate isn't just down, but removed, 40-100 pounds are no longer being dragged around by your truck. That will improve fuel economy.
    Like the old quesiton, which is more efficent A/C or window ventilation...the answer depends on speed. As low speeds, the loss of weight from the gate being down is the primary factor & you should see an improvement in fuel economy. At high speeds, the extra drag created by the turbulance will be in control and you will probably see reduced fuel economy.

    With the bed full, and the gate up;
    1 & 2 become questionable. What is in the bed may change the aerodynamics to make them turbulent. In this scenerio, covering up the bed (or really the non-aerodynamic cargo) can improve fuel economy.

    With the bed full, and the gate down
    ? too many variables; between possible turbulance, difference in weight, etc, there really isn't a single answer but same ideas apply; At highspeeds, turbulance will have more effect & at low speeds weight will have more effect. However as an addtional note, a cover combined with a down/removed tailgate can sometimes produce a nasty vortex in the rear of the truck bed that may cause small loose items to be blown out and can also reduce fuel economy.

    The last thing I'll mention was the economy winner for mythbusters, a net tailgate. It should have produced similar effects to having a tailgate without the weight penalty of dragging one around. If they are strong enough to hold your stuff in the bed, they are a great idea. However it should really matter if they are a net or a solid cloth/plastic design as long as they don't do one thing...flap. Flapping indicates that turbulance is occuring & can actually allow the turbulance to occur, so make sure they are tight enough to stay mostly ridgid.

    I have a few friends who are contracts and they have to carry arround all their tools in custom made boxes in the back of their truck...Usually very heavy and their economy is terrible, but its great to see somebody in that situation trying their best to increase economy. You never mentioned it, but what is the reason you are trying to improve mpg? If its either $ or green factor, making hardware changes may not be the best idea since you will have a long time recouping cost and whatever gets replaced may not be recycled completely. If you just long for great numbers, who am I to get in your way.

    Best of luck!
     
  13. lightfoot

    lightfoot Reformed speeder

    Another thought: it seems that you are paying a heavy penalty for that once a month you have to haul 2000lb. Would it be possible to have that load delivered or handled in some other way (for example piecemeal on succeeding days if it fits into your daily route)? A trailer? If you could avoid that load on your truck, you might manage with a smaller lighter truck.
     
  14. SlowHands

    SlowHands Hypermiling Ironman

    In another thread about a week ago I listed a web page that had info on wind tunnel tests done on full size trucks with 6' and 8' beds. On 8' beds a full tonneau cover was best, and it sounds like you are there already. Over on gassavers.org there is a thread for aerodynamics, and take a look at a Dodge pickup that is aero modded.
     
  15. brucepick

    brucepick Well-Known Member

    As for aero mods, do a google search on
    Phil Knox pickup
    or
    Phil Knox Toyota

    It's worth looking at.

    Are your tires "highway" tread or off-road knobby things? Smoother tread design will help mpg.
     
  16. warthog1984

    warthog1984 Well-Known Member

    re fuel economy vs rpm:

    low rpm is not necessarily the best fuel economy. The lowest fuel consumption vs torque is what your looking for. Example: accelerating at 2mph/s and cranking 1600rpm is better than 1mph/s and 1000rpm.

    Throttle pressure is an indirect gauge of torque. The best way to increase the fuel economy is either get a ScanGauge or check your tach and run at the lowest rpm/unit speed. This may not be the lowest rpm possible. For example, my 4th gear kicks in at 55 but its most efficient speed in 60-65 even though the rpms are higher because the rpm per mph is lower. The calc is (RPM/Speed) and you try for the lowest quotient.

    Good Luck.
     
  17. Shiba3420

    Shiba3420 Well-Known Member

     
  18. endura

    endura Member


    It's my business and I am, unfortunately, stuck with this type of vehicle. I am doing this because I grew up driving small cars and I like efficiency. I had a honda crx and enjoyed driving that more than my friends mustangs/camaros. then I got a toyota echo hatchback and loved that too. This is not about money for me, I just find it personally offensive that I have to put up with 13mpg. All my friends bought the same type of vehicle but 4X4. They use the 4wheel drive maybe 2 or 3 times per year. Their mpg averages around 10/11mpg. Each 1mpg I can raise my average is only another $400/year in my pocket, which in my business is a drop in the bucket. I'm not trying to sound high and mighty, that's just how it is.

    this is personal with me. If I analyze it rationally, logic has nothing to do with it.
     
  19. Chuck

    Chuck just the messenger

    Been driving a CRX since 1985
    • 86 CRX HF
    • 88 CRX HF for 250,000 miles
    • 2000 Insight (essentially a radical makover of a CRX)
     
  20. endura

    endura Member


    I'm not sure I follow. My TQ locks in 4th gear and holds consistently at 1200RPM at about 35mph. Isn't this my optimum fuel economy speed for this vehicle in its current configuration? Unless you have a CVT, how are you changing your RPM/speed equation in top gear?
     

Share This Page