5.4L Super Duty 20mpg at 70mph
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Well that’s what I’m shooting for. I just bought a 07 F-250 Crew Cab Short Bed 4x4 with a 5.4L automatic. I haven’t checked to see what the gears are yet. I drive about 90% highway with the cruise set on 70. I live in west <ST1Texas </ST1so the there will be no mountain driving to through off the results. The test strip will be from a gas station in <ST1<?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com</st1:City>Lamesa, <st1:State w:st="on">Texas</st1:State></ST1 to the gas station where I turn to go to my house. Approximately 65 miles apart, this drive will be 99% highway with one traffic light near the gas station in Lamesa which I might get stopped at. Otherwise, there is nothing to skew the results except for maybe wind, which results affected by wind will be recorded but not counted. Currently the truck is in stock form with the exception of a grill guard, and window sun visors.
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Currently the truck gets 13.2mpg in stock form with 120,000 miles on it. So I’m looking for suggestions on what to do to increase the mileage. I will be starting with the least expensive upgrades first and working my way deeper into my pocket book. I would appreciate any suggestions and first hand experience. If you feel the need to leave messages like “it will never happen, buy a Honda, or keep your foot out of it” I don’t care to hear it. Constructive comments only please.
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First things first It needs a tune up.
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Sparkplugs
I’m going to go with stock unless I can find some credible evidence that one is better than the other.
Oil
5w-20 motorcraft I guess
Filters
Wix
Service transmission
The usual filters and flush
UPGRADES
Air filters?
K&N or Amsoil or others if you have had just amazing luck with something else.
Cold air intake?
Probably not going to do this one unless someone can show me some hard evidence of one that works that much better than stock <O</O
Fluids
All amsoil in all gear boxes, transmission, and motor <O</O<O</O
Electric cooling fan?
An electric fan out of a 97 thunderbird is 18.5’’x 24’’ and I have heard good things about this upgrade to the tune of 1.5-2mpg, but that’s in a navigator. This project should cast about 100-120 bucks <O</O
Headers?
Any suggestions <O</O
Y-pipe
Anyone got a great aftermarket one they recommend or is this a part any reputable shop can build. <O</O
Catalytic convertors
Need some opinions on the stock ones vs. aftermarket, high flow, how many do you need. <O</O
Muffler/ Exhaust
What size pipe should I use? I’ve got a good shop to use but I would like to hear what everyone else has liked or disliked <O</O
Headers/Manifolds
Are they really that much better than the manifolds?<O</O<O</O
Bed covers/Camper shells
I’m not opposed to either if someone has one did you notice any better/worse mpg when you put it on?<O</O<O</O

 

I replaced my spark plugs with some platinums
I use Royal Purple synthetic
K&N Cold Air, K&N Oil Filter, and Wix Fuel Filter
Magnaflow Hi-Flow Cat and Thrush Welded Muffler (most noticeable upgrade)
It doesnt seem to use near as much fuel as it did before but I've never calculated before, it is ALOT easier to drive now though, alot better throttle response.
SPDperformance.com has y-pipes for our trucks, $100 for aluminunized, that'll be my next mod pretty soon, and as for the manifolds, I'm too scared to break off a bolt so those are staying, lol. BTW mines the 2v 5.4

 

Shouldnt be hard in those conditio s. My 5.4 usually gets 14-15 but if i run all highway and it will get 18-19. On flat 20 shoukd be doable


I think the only mods to really help would be reducing weight, drag (lower truck, bed cover), and highway tread tires of the right size. Those could make a big difference added up

 

What tire size are you running?

I recommend a skinny tire at max air pressure for optimal MPG.
Keep the windows up and A/C turned off.

You will get lots of opinions on K&N air filters and some of those offering opinions have even used K&N's.

Personally, I use K&N air filters and Lucas Fuel Treatment bought at Wal-Mart or auto parts stores. I consistently see ~1.5-2 MPG increases for each, so about 3MPG increase using both. My wife's Mazda MPV van really benefits from the Lucas.

 

It will never happen, buy a Honda, or keep your foot out of it!!

That is not an option in west Texas.

To the OP: Do not change your catalytic converter. It is illegal to tamper with them unless they are faulty. Changing them will not benefit you anyway. Watch the exhaust work that you do, as it can actually reduce your torque with less back pressure.

Headers might be better, my 5.4 SD I had had a leak in the exhaust where it connected to the downpipe to the cat and it couldn't be fixed without swapping the manifold. You will get better flow to the cat, which might increase your mpg buy half a mile or so.

Electric cooling fans being better is a myth. Don't buy into the hype. It will do no better than your stock fan, and in some cases it will perform worse.

You could get an intake for better airflow to the engine, but it won't be a drastic change in mpg.

Amsoil is good fluid, that is probably the best on the market for long-term durability, but for your purpose of mpgs, it won't do much more than any other high quality fluid.

Replace the spark plugs.

I would use Motorcraft oil and all Motorcraft filters.

I think your truck will get 20 mpg in the situation you are describing with just regular maintenance.

 

With your current setup at the speed you want to run I do not forsee you achieving your mpg goal. Maybe if you slow the speed down and drive really easy you will get closer. Best bet is to keep the truck stock but well maintained. A custom tune tailored to fuel economy will help also.

 

Sure it is. Drive naked and mist yourself with cold water.

Just don't post any pics!

 

Cutting torch, don't forget that. You can start cutting sheet metal till you get it light enought to get 20 mpgs.

Seriously, slow down to about 60 mph and that will help the most.

 

Find some gasoline without ethanol. Back when I could stil buy pure gas my 5.4 did much better than with the ethanol laced fuel.

 

I'm always skeptical of the MPG numbers people post on here. They always seem too good to be true. I don't think you will be getting 20 MPG with a crew cab 5.4L SD. You *MIGHT* be able to hit something like that with a regular cab with smaller tires and the 3.73 gear ratio package. Keep in mind this is a big *** truck so your expectations have to be realistic. I have an 09 250 5.4L Crew Cab shortbed with the 4.10's and the factory 20" wheels and I love the truck but I didn't buy it for the fuel economy. Most of the time I'm driving around with my SCT performance tune and I get between 11 and 13 depending on how psychotic my driving habits are. It's absolutely CRAZY how much the RPM's affect the MPG on my truck. If I'm out there with a heavy foot the instant MPG usually shows approx 10 . But if I'm very light on the acceleration and use cruise control I can get in the 15-17 range. I drove to work last night in a hurry and got 10.7 MPG, but I've driven the exact same stretch of road and gotten 15 mpg so that shows much much a difference the acceleration and RPM's can make on fuel economy.

Two weeks ago I made a highway drive out to Wasilla which is mostly flat but has a few grades of note. Before I left I reflashed my PCM to stock. When I arrived my trip computer showed 16.8 MPG which I was happy with. That was mostly highway miles @ 65 mph.

Again, YMMV depending on road conditions, driving habits, and your specific vehicle configuration but just remember, its a 3/4 ton gas truck, be realistic with what you can achieve. I know when I bought mine I was only expecting 15 mpg and I know I can get within +/- 1 of that if I watch the way I drive so I'm satisfied with mine for now.

 

I know on my 7.3, I set the cruise control to 65 (on 60 mph roads) and I get about 16. I try to keep the RPMs south of 2K, around 1800-1900.

 

I agree, lots of people will post numbers just to post numbers. With no description of what the conditions were when they got those numbers, if there even real. It’s kind of sad to see people try to brag or just flat out lie to total strangers just to look knowledgeable on the subject. Your right, 20mpg is a lot to get out of this truck but better to shoot for the moon and miss than to just sit around and gripe about the price of gas. If I end up with a consistent 18 that’s still a considerable improvement.

 

Bolton Oil in lubbock, Tx still sells gas with no ethanol but I'm looking for modifications that will increase mileage

 

GOOD LUCKY. You not going able to get that without invest tons $$ IN.

My suggested get vacuum gauge on and keep 15 psi or higher. Cruise Control made worst. Use your naked foot control gas pedal and watch vacuum gauge will get you 16-20 mpg.

Speed 70 mph It hard for that truck. Lower to 60-65.


My old 01 F250 5.4L 2wd reg cab we got 16 mpg on speed limiter 93 mph all way. That with my foot on and MAX AC all way for 600 miles in 98oF outside.

I would say you would get 17-19 mpg but it get tons patience.

Put stock tire that are SKINNY and put psi 65 in front and 70 psi in rear. 80 psi would do but it make tire's middle tread get short quicker.