more about fuel milage?!

[cantspell]

Hello,
So i'm been having chronically bad fuel milage. I"ll first give an update.
I have done a full tune up and a fuel injector flush, only think i didn't do very well was clean the MAF, but i did it which i'm sure is better than nothing. I also has the computer reprogrammed for my tire size, which is 31",however i'm sure after disconnecting the battery, this was 'undone'.
I have a magnaflow and filter on (which i know will reduce economy). And i have 3.55 gears (which suck) and a bush bar on the front.
I am getting about 325km to a full tank, or about 200mi. With mostly city driving and unfortunatly it's usually very short trips, is this normal?I"m essenttially getting just over 12mpg??? What gives???

Assuming my engine is running well, which both I and the Ford dealership say it is. And taking into considerations that i have adopted a conservative style of driving . In fouth gear (with the over drive off) at 65mph i'm at about 2600rmp, which i know is high, but I can't possibly lower my gears, as i already have 31" tires on and acceleration is slow (and when i measured the speed, i took into account the variance the tires produce). So what is it? any ideas?

I think, some of it could be due to the performance air filter and exhaust, however, I also think that a change to my gearing might help, but considering my already over the 'ideal range' - what should i do? Swap out my magna flow?
pls help! Matt.

 

[Alec]

It's probably just the nature of the type of driving you do. Here where I live for school, I get an avg of about 12 mpg city. However, when I go visit my parents who live in a different city, I get about 14 mpg city. If you drive mostly short trips with the truck cold, you will get crappy mileage.

The intake and exhaust probably don't have much of an effect on your mileage, unless you drive stop-and-go and like to accelerate hard all the time.

 

[Sallad420]

I just figured out my 96 XL fuel useage. For about $65 (CDN) of gas, full tank, I get about 450 km out of that. I also have 31" tires. I don't know what kind of gears I have, I've only owned the truck for a whole week now.

Question... why do you drive with the O/D turned off?

 

[Alec]

To properly measure hwy rpms at a given speed you should be in your 1:1 tranny gear, which is 3rd in an A4LD or 4R55E or 4th in a 5R55E; "D" with OD turned off.

 

[cantspell]

Sallad420 - pls tell me your do maintly highway driving. I think i get about 350km MAX on a full tank, though my tank takes about $52 to fill (but i'm sure that's not hte size, but the difference in fuel prices, it's about .76 over here).

Even though my rpm's are a little high in my 1:1 hear, I have to think it's the gearing.
b
Also, as i think about, and if anyone has any info on this let me know. A few months ago, i had a leak in an upper plastic vacume hose, it was actully where it joins that at a ruber 'Y' type thing that's beneath the plastic intake shroud. They replaced the house, but I"m not sure if there isn't somethign wrong with the rubber 'Y' piece - i'll check.
What sort of affect would a upper intake vaume leak have on fuel economy?
p.s. - I've had them check my fuel pressure, and it was fine/within spec.

 

[Rhett]

If you have a lot of hills where you live, it will also reduce your mileage.

The engine on my truck is running fine (new O2s, etc.) with the exception of some carbon build up (soon to be taken care of I hope) and still I only get 13-14 mpg in town, 18 mpg on the highway--that's with a 4.0 V6, 3.27 gears.

 

[Sallad420]

I haven't gone Highway driving yet, so I am getting between 400 -450 km in the city. That's just driving to work and back, lots of stops along the way.

Gas here is 87.4 a litre. (Our gas went up because of our Olympic bid going on in Vancouver for 2010)

I've filled it twice now, first time was $65 for about 410km, second time was $67 and I got 450 km out of it. That's about 75 litres of gas.

...from what I've read, that's about average. It's about 16 MPG.

 

[cantspell]

Well, i figured it out, it's the exhust! Specifically the muffler, it's a high flow magnaflow that i have on and it's killing me....well at least my pocket books. I had a nice long chat with a ford Mechanic, and the exhuast, combined with the 31"'ers are killing my fuel economy - so i guess it's back to a stock setup...

 

[Alec]

Unless you drive with a 200 lb right foot, the exhaust is not going to kill your mileage.

It is not your muffler, it may make a 1/2 mpg difference, but not more. You will most likely not fix your problem changing it back.

 

[rydinhigh]

dont worry about the exhaust i have an aftermarket one and still get 16mpg

 

[IAmTodd]

I've also noticed that in cold weather the MPG is worse. Just by temperature change, i got 4mpg back, and that was also by taking me ski rack off.

 

[Rhett]

In cold weather, many gas stations sell gas that burns cleaner in the cold air. The downside of this is that it can hurt your mileage.

That's why you might notice you get a little better mpg in the summer as opposed to winter.

 

[jwrezz]

I don't get it! All else being the same, a better breathing engine should get BETTER mileage! Unless you love the sound of that open intake, and exhaust so much that you gotta hear it all the time. Then you're screwed, cause that kina driving WILL kill your mileage. I have 3.55's, 31" tires, 4 speed od. My commuting is 22 miles of mixed driving (10 mi on the interstate, 12 on local roads). When I'm a conservative driver, I get about 14.5 mpg. When I'm a bad boy, or take a mid tank trip into the woods, I may bring that average down to 12 mpg. But on long freeway trips (I've driven to NC a couple times, to the jersey shore quite often (but many toll stops on that) I get about 16. One time when I was on the freeway for almost an entire tank at 70mph, I got about 20 mpg (420 miles). But yeah, on the whole these trucks get pretty crapy mileage. 14.5 is what I'm used to. I make do. Adios...

 

[aldive]

Originally posted by Alec
Unless you drive with a 200 lb right foot, the exhaust is not going to kill your mileage.

It is not your muffler, it may make a 1/2 mpg difference, but not more. You will most likely not fix your problem changing it back.

I picked up over 2.5 MPG when I went with a cat back,.

 

[Robert]

jwrezz - You could easilly pick up a couple of MPG if you'd re-gear to 4.10s to accomidate your 31" tires. My '97 came stock with 30" tires and 4.10 axles. Although I have a SOHC, I consistently got 16 MPG in the city, 19 MPG on the highway. Now that I have 33" tires, my mileage has dropped a couple of MPG with my 4.10s. You are running your engine below it's optimum power band so it uses more mileage than it would if you could increase the RPM a bit. I don't know what size tires yours came with stock, but I do know they weren't any taller than 235 75R15 (28.9"). Since you have 3.55, it probably came with shorter tires than the 235s. If yours did come with 235s then the ideal ratio to keep your engine in the power band that Ford designed into it, you would need 3.80 axle ratios. That leaves you with two choices, 3.73 or 4.10. If your tires were smaller than the 235s, then that would move your ideal gear ratio closer to the 4.10. Of course it would take a long time to pay off a gear change at the 2 MPG you are likely to pick up. Then again, you may extend the life of your $2500 transmission or your engine.

 

[IAmTodd]

So what is the "optimum" RPM for each engine?

 

[Alec]

For mileage, probably cruising at around 2200-2500 RPM.

 

[jwrezz]

Stock size was 235/75/15.
Now w/ 31's (actually they measure just over 29 inches tall) at about 75mph I'm at about 2500rpm (OD). Does this sound about right? Maybe I have the 3.73's? I know they aren't 4.10's. Is there an axle code on the door jam? But any way going from 235/75 to 31's doesn't seem like it'd lower my operating range enough to lower my mileage. The tires are only slightly larger w/ would lower my rpm's thus raising my mileage (is my thinking off)?

Thanx,

 

[Canada91Ex]

East coast MPG

hey there cantspell

out here in halifax I am also only getting 350km to a tank. I jus cleaned tthe MAF and IAC so I am hopeing that helsd a little. The X is stock with no mods but has almost 200000K on the engine. Gas gos for about 81.5 here now down from 86.9 last week.

hoping warmer weather and a tune up (in the near future) help get the mpg up soon.

 

[XLT Xtreme]

Well guys doing a mixed amount of driving, city and highway I get around a avg of 20mpg. Just filled up yesterday and checked it. In the winter during the same driving I was only getting 12mpg.