Hey guys,
Im a little upset and could use some advice. A few months ago i purchased my first diesel truck, a 99 f-350 crew cab dually, 2wd with the 7.3. The first couple tanks of fuel i ran through the truck i had an average of 13.5MPG. So i got on the web and started doing some homework on how to improve my mileage. I went and bought the afe stage 2 intake, a 5 inch turbo back exhaust system( witch is incredible) and a edge system with the attitude display. I installed all of these things without a problem. This past weekend i took the truck on a trip up north pulling a small aluminum boat. Mostly all highway driving i was really excited to see what kind of mileage numbers i would get. After checking my first tank i found out im getting 13.5MPG!!!! Nothing changed! If anyone has any ideas on this Im dying for some help. I feel like i spent all this money for nothin. Im hoping theres something small i need to do, fuel filter change, transmission, etc. Something ive seen guys on here with most of the upgrades i have claiming 20-24 mpg. Thanks in advance for any help

 

Hate to say it to ya, but most of the time adding that stuff doesnt affect your mileage. Just makes it funner to drive. A few tips, make sure you EBPS tube and sensor itself are clean of soot. Keep the RPMS under 2K, make sure you air filter is clean. Check for leaking up-pipes. Check/replace your fuel filter. Few people get in the 20's for mileage and they are manuals and 2wd. You have 4.10 rear gears which is making it worse also.

 

What John says is true. There are a couple of other items to check as well, and you mentioned one of them yourself.

- Go ahead and change your fuel filter. Stick with the OEM Racor brand filter.
- Check your tire pressures. Low pressures can kill mileage more than you might think.
- Change your oil. Consider a 5w40 synthetic. I've seen excellent results in mine with the 5w40.
- Check your intercoller boots to make sure you're not losing any boost pressure.
- Be careful how you calculate your MPG. Fill up to the neck with every fillup and calculate your mileage by hand... nu use in using the overhead lie-o-meter, if you have it.
- Check your speedo to see if it's accurate. Best and simplest method I've found is getting on the highway when traffic is low volume, setting the cruise on 60 mph , and use highway mile markers to time your trip for exactly 15 miles. Keep in mind that for this to be really accurate, you have to be right at the cruise setting for the entire time. Other folks have used a GPS to cross-check their speedo's.

These 7.3's get really thirsty above 2000 rpm with 3.73 gears, and your sweetspot will be a little different since you have the 4.10 gears.

 

If all the mileage claims were true, I'd have to be approaching 30mpg. Things I have learned:

I started out at 16-17 mpg.
Running a fuel additive would get me 2-3 more mpg.
Intake was supposed to get me 1.5 more mpg.
BTM should add another 1.5 mpg.
AIH delete? Should get me 1 more mpg.
I read that synthetic 5w-40 motor oil is good for 2 mpg.
A good economy tune will gain me 2 mpg.
HPX line would get me .5 mpg.
Hutch and pre-pump would get me 1 more mpg.
Full regulated return system = 2 more mpg.
Wicked wheel will gain me .5 mpg.

So after 3 years of modding I am happy to report that I am still able to get 16-17 mpg.

Always remember that most of the mileage claims are ways to con our wives into letting us spend more money on our pickups.

And don't believe everything you read on the internet.

 

Yep, I'm in the same path. I should get at least 25mpg in the city now! But I'm getting 14mpg, WOT after every stop.
If all the basics are OK, the mileage won't go up with any of the nice mods we are adding. 'cause you're automatically driving it like you should as using more power etc. Leaving all the "rice burners" and do I dare to say it, Chevysbehind in every lights
I can't drive like max 2000rpm, you can't hear the engine and it goes like retarded, everyone thinks you are driving PSD stock

 

Sorry boss... adding fuel will not increase milage... just doesnt happen. If you want good milage then get a Honda... 13-16 is great for a rig that weights 6000-8000#'s

 

It doesn't sound like a waste of money to me. It sounds like you improved the sound and performance of your rig. That turbo spooling up probably sounds fantastic. Enjoy it.

 

my whole life my very smart dad said there are two things a man will always lie about.
(1) the women he has been with.
(2) his fuel mileage

 

Your Dad sounds like a very profound man.

 

that is funny....



the only way to get good mileage is to keep your foot out of it...

 

Sorry but you purchased nearly the worst configuration for fuel mileage. It would be harder to see 13 mpg while towing if you had 4wd. Your problems are that you are driving a very heavy, non-aerodynamic truck that is running at higher RPM's down the highway than most others. The DRW's came with the 4.10 rear, so when you are at highway speeds you are turning well over 2000 RPM's. That is the magic number on these trucks for fuel economy. Your best bet is to either suck it up and pay the fuel bill, or slow way down and keep the RPM's below 2K.

BTW, very few trucks will actually get much over 20 MPG hand calculated. The single cab 2wd 6-speed trucks can reach that marker way easier. If you have DRW or 4wd, that's the nail in the coffin for you. Try as I may, I have never quite reached 19 MPG on the highway, although I did come very close many times.

 

You may not be getting better mileage just driving down the road but, if you check on it while towing a heavy load, you may see an improvement there. I put over three grand in my F-350, it burns rubber and sounds great but the mileage went down. Now when I tow my 20 ft box trailer, it will go to the speed limiter [95mph] no problem and the mileage is even worse! But it sure is fun!!

 

Let me tell you guys how I went from 13-14 mpg to 18.2 down and 18.5 mpg's back from our OuterBanks trip a couple weeks ago. It was really simple and made me realize how much our trucks respond to our right foot. The answer, take my wife, (please, just joking), listen to her gently remind you of how fast you are going, kindly asking why did you take off so fast, inquiring as to why you need to pass everyone on the road, lovingly reminding you that your insurance is high enough now without another ticket. All of this combined did indeed save me 4 to 5 miles per gallon. And yes I do know the proper way to check mileage and double checked myself. The moral is your foot is what is going to save you fuel, not your wallet and mods. My strait exhaust would probably help if it didn't sound so damn good. My programmer would help if it wouldn't spin tires, ect.....

The trip is long over and mileage is back down to 13-14 range, driving excitement is back to normal, and the black smoke is again rolling, and I don't mind stopping by the fuel station a little more often.

 

Also one thing to consider is average speed traveled for the tank of fuel. Arrow dynamics play a huge role if you are trying to get anywhere fast. Where I am at, freeways are 75ish and highways are usually 65. Due to the wind drag if I keep it at 60mph or so, about 1700 rpm with my 3.73, I can get the 20mpg some claim, but driving that slow sucks, you get a lot of 1 finger solutes to those who obviously slept in or just have way too much coffee in them to think, hey that guy is getting 20 mpg in a truck twice the size and mine. Moral of the story, RPM and wind drag, the faster you want to go, the less mpg you are going to get.

 

Haha, they dont give me the one finger salute, because i think they are afraid of what might happen. They can't see the driver and as far as they know, hes a tall guy since you need to be tall to hop in my truck. I drove 300 miles going 55 mph on the freeway once, because i had nothing to rush home for. I got my all time best of 17mpg. I have never seen that since. Im gonna try for that again this summer.