I have a 06 F-350 KR and i have all my mods listed in the sig below i think. The reason for this post is i just put 2 new injectors in and my fuel mileage dropped from 13.5 to 12.5 on the highway. is this normal for a period of time? i remember before i had injector problems i was getting 16 and since then i havent been able to touch that on a down hill run with me on the brakes. i know the lie o meter isnt always accurate but i also like to see some good kinda numbers on there too. Thanks in advance.

 

ok so my sig didnt come up. so here they are: 2006 Ford F-350 4x4 King Ranch, ARP Head Studs, ITP RR, Airdog 165/75, afe intake, 5" MBRP Turbo Back Exhaust, SCT TSX with tunes by TSD and MATT, ERG delete, 2" leveling kit, 35" Nitto Trail Grapplers, RECON cab fender tailgate mirror lights, harley headlights, 08 taillights

 

Since you have tuning, I wouldn't trust the lie-o-meter at all. If it was trustworthy I would be getting 22 mpg instead of seeing the same numbers that you are.

Now it could be winter fuel, I do see one item in your siggy that has been known to cause lower low end TQ without the mods to support it and that might also affect MPG as well. I can't really say too much though, because I don't have a timeline for everything. I just know that you had decent mileage before the injector repair and now you don't.

Before you start sweating as to how good or bad you are doing in the mileage department, I would start hand calculating your numbers, because like I said I wouldn't trust the lie-o-meter on a tuned truck. It might be spot on or close, but until I see a few hand calculations I wouldn't trust it.

 

You should also try using a GPS handheld to verify that your
speedometer AND odometer are close (or not).

Even hand calculating isn't any good if the odometer says you
went 200 miles but you really only went 125.

 

what is that?

 

Either way, it's all relative, right? The lie-o-meter will still tell you whether you're doing better or worse than your last trip (or whenever you reset it). Same goes for doing the math on a napkin... as long as your odo and speedo haven't changed since the last time you figured it, you'll still know if you're doing better or worse.

That said, using a GPS is probably the only way to get the mpg to be truly accurate. Even then, you have to use the same fill-up techniques every single time, otherwise you'll be missing out on a few drops of diesel and it will throw your calculations off. For instance, if you usually fill the tank up until it spits out of the fill tube, and then the next time you stop fueling when the pump clicks the very first time, you could be missing a half gallon that you usually have in your tank and thus calculate higher mileage than you really got.

Sorry for rambling....................

 

Not exactly true all the time. My mileage hadn't changed since all my mods, however, the lie o meter shows that I went from 16(which I only hit once) to 22 and yet my average is the same. As if I never did any performance modding at all(which I think of as a good think since I could easily see it going the other way versus getting better).

OP: The 5" exhaust is what I was alluding to earlier. Too much pipe and not enough air/fuel to flow through it.

 

Very interesting. Looks like I need to start doing the math on every tank.

 

Now, I might be the fluke as well. Just because it happened to me doesn't mean that it would happen to you or the next person. It might take 100 people before that type of scenerio happen again.

The joys of MPG calculations are just bountiful.

 

I have never hit 16 on the highway and am satisfied if I see 14 to maybe 15, usually drive speed limit or under.
Pulling 15,000lb 5th wheel on mostly slightly hilly ground will get 9 to 11mpg...that said I am not dissatisfied as I did not buy a 1 ton dually for good mileage. rear end ratio is 3.73..

I figure that so far it has been trouble free, except for FICM on warranty, that more than makes up for better mileage..

 

I just hit it once and that was on a road trip running empty. 682 miles one way doing 62, I was trying to get as best as I could get without going crazy on a road trip doing the speed limit takes 10.5 hrs. 4.30 gears on my rig though. Might have done better with your gearing on the highway.

 

ive got 4:10 gears and i know i will never get awesome fuel mileage being that it is a dually with 35's but like yall have said it will atleast tell me if im doing better or worse and right now its showing worse. i atleast want good fuel mileage with these mods being that its one of the reasons why i bought them. fuel is going sky high so anything that will improve it for a small amount of money is good but after replacing two faulty injectors and then it got worse was alittle strange to me being that common since would tell me it would get better.

 

o and teppler just to blow your mind before i put the 35's on i actually hit 18 mpgs and was truely getting 18 on the highway.

 

I'm sure others get better mileage just the difference between some trucks. I am glad to get one without bad problems even if mileage is less than others..

 

Well I am one for modding one's vehicle as a means of making it your own versus just one of a million others, I wouldn't do these types of mods with fuel economy in mind.

First and foremost, they are performance mods. Even tires are performance mods depending on what you get them for. Although I'm not an a/m tire fan at all, but that's another subject.

It will take many miles and quite a few yrs to make it worth your while for getting those mods for increase fuel economy if you see any at all and that depends on how much you see if you do see it.

Not what you wanted to hear I'm sure, but unfortunately that is the case more often then not.