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Old 05-25-2012, 08:57 AM
bduke23 bduke23 is offline
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Why is my mileage so bad?

My truck is a 2001 F150 with 5.4 auto, 4x4, off road package, and I believe tow package as well. 170 000 km (106 000 miles). Ever since I bought it almost a year ago it has absolutely loved gas... I read all over this forum and the internet that everyone gets 18-21 mpg on the highway with their identical trucks, mine gets 14-15 .

I have done everything I can think of or read about. I drive very slowly, never rev above 2000, usually truck shifts about 15-1600 rpm, and on highway I never exceed 65 mph. I had the dealer change the spark plugs. Cleaned the MAF. Brand new air filter. Synthetic 5W20 oil. Tires are aired up. Put a tonneau cover on the truck (this one actually seemed to help a little, as I expected). I also had a warped exhaust manifold, which I had replaced as well as the studs. I bought a used Diablosport Predator II tuner for the truck.

I am not sure why my mileage is so much lower than everyone else's. My truck is not lifted, completely stock except for the tuner. I have duratrac tires on it now, but had highway all seasons on it before for only about 16 mpg highway. I am sure that most numbers for mpg that get posted on the internet are slightly inflated, but I was expecting 18 mpg out of this truck.

Have I missed anything? I love this truck, but it should be doing better I think.
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Old 05-25-2012, 01:06 PM
slomafarms slomafarms is offline
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The best ive ever got was about 17. But normally comes out to 12-15 with my stock 5.4. If someones got info on getting 18-21 id sure like to have it!
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Old 05-25-2012, 02:13 PM
Bluegrass 7 Bluegrass 7 is online now
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First the 18 to 21 you see 'everyone getting' is not the norm so question the sources.
What you are reporting is more the norm so you have nothing that is a big issue.

My 172,000 mile perfect running 4.6 is at 16 to 17 on the best runs with 14 to 15 short run averages.
Some are going to dissagree but you have to live in reality.
Your running about 4800 to 5000 lbs in weight +/-.
.
Things to check out that may improve the mileage are new OX sensors, check the fuel pressure is not to high, Thermostat is not running the motor to cold.
Run tires on the high side of pressure and be lite foot consious while driving..
Don't even think about super air intakes or filters. They won't do anything for you.
Good luck.
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Old 05-25-2012, 03:09 PM
bduke23 bduke23 is offline
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Ok that's what I thought. I've read through several "What kind of mpg do you guys get?" threads and seen a lot of really high mpg claims, so I am going to assume that those people either aren't actually figuring it out, or are grossly inflating so they feel cool. I know a couple guys who have similar trucks and claim about the same high numbers, but I have always discounted their stories because i know exactly how good at math they are.... One of my friends was telling me about his younger brothers truck, a 99 F150 with 4.6, lift kit, 35" tires and "stock gears" which apparently gets 25 mpg on the highway

Getting back to your O2 sensor comment, I have thought about changing them out, but their quite expensive, and I don't want to dish out a bunch of coin to change all 4 and see no effect. However, I am able to disable my rear two through my tuner I think, so I might try that and see if there is a difference first.
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Old 05-25-2012, 04:08 PM
Bluegrass 7 Bluegrass 7 is online now
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You may be able to zero the rear sensors out of program but it won't do you any good.
Reason is they are cat monitors only and have no input to fuel mileage.
Only the fronts have that duty.
As far as age on the fronts, if they are fault free now, the only possible advantage to replacment would be if they are a bit 'lazy' in response for fuel corrections and that usually is from contamination.
Only way you might know this is watching their ability to 'hunt' using a scanner that can look at live data. If they appear slow from a compare to a known good one or your experience with them, would be the only way to know this.
God luck.
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Old 05-26-2012, 12:02 PM
galaxie641 galaxie641 is offline
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Mileage threads for most are just pissing contests, you are above average IMO, I can only get 13-15 and that is after doing several mods to increase from 12.8. I am sure you can get 18 with a 2wd SB 4.6L where it is extremely flat and you are only going 60mph for long stretches.

Also have to figure there is an extraordinary amount of people that can't calculate mileage for whatever reason, and in the newer vehicles they go by the dash display which is not accurate.
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Old 05-26-2012, 01:50 PM
Bluegrass 7 Bluegrass 7 is online now
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On one board or another , just recently a kat posted his excitement of getting 27+ mpg on some mods done.
It was based on just 9 gallons of fuel use after the first road usage.
Claimed no codes or unusual drivabilty.
This just does not happen on a nearly 5000 lb 'brick' on wheels with an 'engineered' system that runs on a computer program when the only way it runs is on inputs from sensors and the basic motor design and displacment.
Only way for mileage way out of the norm is to run the motor very very lean and that would trigger lean codes from the X sensors that are calibrated for oxygen detection in the 14.6 area and won't allow it normally.
Bottom line is you can't influence the whole setup as designed, by changes on the outside of the system to very much of degree.
Remember one item if nothing else, the throttle body plate opening by foot control is the sole way the motor power is controlled by varying the motor's volumetric efficiency.
At normal cruise speeds the throttle is not open very far so that means any attempts to add air, or reduce airflow restriction, in the input tract ahead of the mass air and TB has no effect at any point except above about 7/8 throttle, then it may still not be of any benifit on a stock motor.
Mfgers can claim airflow increases with their filters which are probably true but you can not use them to any benifit for fuel mileage.
Have a good holiday.
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Old 05-27-2012, 01:47 PM
dilas dilas is offline
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Nah... yours is the norm. I got 14-15 on overall average with the 2002.

I drive conservately with egg on my gas pedal. I lost about .5 mpg with slightly beefer BF Goodrich TA 285/70/17 tires. Be happy.... Don't worry about gas mileage too much unless it dips into 10-12's.
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Old 05-28-2012, 07:18 AM
enriched&beyound enriched&beyound is offline
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1st I'll agree/echo that you're getting pretty good MPGs for typical daily driving for this time of the year.

How many miles are you driving on a daily routine? what kind of miles are they, mixed, all highway, etc?? What is your gear ratio?

Only other thing that "may" help in increasing your MPG's that you haven't mentioned is to clean the throttle body housing interior . Not sure if you had done that yet?

also, another mod maybe to go to electric fans, that reduce the constant load on the engine, thereby giving the opportunity to increase mpgs. but this also can be kinda spendy & have a prolonged payback on the investment, especially if you get a kit. If you watch the salvage yards you can get this much more economically.

I did see a minimal increase in MPG with just replacing the front two O2 sensors , but that was my situation, you may or may not see it. another word "individual results may vary".
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Old 05-29-2012, 11:47 AM
bduke23 bduke23 is offline
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Ok well now I don't feel so bad about the mpg. Even better, I can confidently tell my friends to STFU cause they don't know what their talking about!

I have thought about electric fans, partly for freed up power, partly cause it would be cool, partly because I go crazy if I have nothing to tinker with. There was a used Flex-a-Lite Monster setup that came up for sale near me recently, but for the cost of gas for me to go pick it up, plus cost of the fan, it wasn't a much better deal than to just buy new and have warranty. Someone mentioned to watch junkyards, what kind of fan would I be looking for? Would the e-fan setups from the newer F-150's work?

And no, I have not tried cleaning the inside of the throttle body. I only went as far as the MAF. I suppose I could pull it all out and take a look though, perhaps on my next due oil change when I will also change air filter again.

To answer an above question, my trips are nearly all city, and then one or two shorter highway trips... combined I usually get around 14mpg, so I am assuming about 16 straight highway, 12 or so straight city. This will have dropped some recently, as I mentioned I got much more aggressive tires put on and haven't quite gone through a tank of gas yet. Typically I drive about 10 km on a cold start to work, then 10 back again. When the weather cooperates I ride my motorcycle as much as possible. Oh, and gears are 3.51 I think, stock 265 tires.
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Old 05-29-2012, 04:22 PM
enriched&beyound enriched&beyound is offline
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Quote:
Originally Posted by bduke23 View Post
Ok well now I don't feel so bad about the mpg. Even better, I can confidently tell my friends to STFU cause they don't know what their talking about!

I have thought about electric fans, partly for freed up power, partly cause it would be cool, partly because I go crazy if I have nothing to tinker with. There was a used Flex-a-Lite Monster setup that came up for sale near me recently, but for the cost of gas for me to go pick it up, plus cost of the fan, it wasn't a much better deal than to just buy new and have warranty. Someone mentioned to watch junkyards, what kind of fan would I be looking for? Would the e-fan setups from the newer F-150's work?

And no, I have not tried cleaning the inside of the throttle body. I only went as far as the MAF. I suppose I could pull it all out and take a look though, perhaps on my next due oil change when I will also change air filter again.

To answer an above question, my trips are nearly all city, and then one or two shorter highway trips... combined I usually get around 14mpg, so I am assuming about 16 straight highway, 12 or so straight city. This will have dropped some recently, as I mentioned I got much more aggressive tires put on and haven't quite gone through a tank of gas yet. Typically I drive about 10 km on a cold start to work, then 10 back again. When the weather cooperates I ride my motorcycle as much as possible. Oh, and gears are 3.51 I think, stock 265 tires.
seems like your doing pretty well with only ~6.2miles one way to work.

use search of electric fans,

Ford Truck Enthusiasts Forums - Search Results

Installation Guide: Mark VIII E-Fan, '99 F-150 4.2 - F150online Forums

How To Install An Electric Fan

I thought I read somewhere that some one got twin E-fans from a Taurus that worked too....can't locate that right now
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Old 05-29-2012, 06:44 PM
19fifty4 19fifty4 is offline
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I think your mileage is in the ballpark. I get slightly better but have a 4.6 and drive like grandma.
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Old 05-29-2012, 06:51 PM
vista461 vista461 is online now
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I have a 4x4 5.4 01 Screw, Off Road pkg with 3.55 gears and 265/70r17's. My normal highway mpg is 17ish, but on a trip to OH and back I got 20 both ways, but I was on a turnpike most of it so it was very flat. Going to NM last year I had a high of 19.6 and a low of 15.5.
I usually get around 13-14 with the city/some highway mix.
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Old 05-30-2012, 12:44 PM
amac2013 amac2013 is offline
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All of yall with yalls high gas mileages..... I drive a 2001 4x4 5.4 ext. cab, 4in lift, 33in tires and I only average 11.5 mpg on the highway
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Old 05-30-2012, 09:42 PM
TwoMidgetsTall TwoMidgetsTall is offline
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Oh so I see we have pissing contest for lowest mpg here... Bought my truck with 47000 miles on it ('03 Scab 4x4 4.6L and 3.55 gears) was getting 16-17mpg as purchased. Finally went to replace the tires and found that I had been rolling on 225/60R16 which incidentally are not stock size (235/60R16). Replaced them with 285/75R16 and dropped to around 14-15 mpg. Got back from Afghanistan in Sept and lifted 4" threw 35x12.5R17 on it along with long tube headers w/high-flow cats, SI/DO Borla catback and a programmer; I now get a grand total of 11-12.5 mpg.

amac2013 still beats me
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Old 05-30-2012, 09:42 PM
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