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Voice/Data Guru
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Yep jeremy yours seams to be on the right track for 20 or so . mine was a 1k round trip and I put in 92 to 93 the hole way.
 

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Premium Member
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2,545 Posts
well I just got back from a trip to Tacoma/seattle. first the car

96 Tbird
2002 4.6L With 01 Bullitt Intake
90mm Lightning Maf, Dynomax Cat Back exhaust, PI 3500 Triple Torque Converter, Dynotech Drive Shaft, EGR shut off
Engine has about 45k on it now
3.73 Cobra Rear End

On the way there I drove about 73-80 the whole way there except one stretch where it was completely flat and open And I went ahead and gunned it and cruised at 130+ (GPS) and after I got to tacoma I went and filled her up and avg a 21.233 MPG

On the way back it was colder but decided to set 140 in the GPS max speed plus I had to do a little city driving to find some dinner and a bathroom so that one avged about 22.5 MPG I think I could 27-28 out of her if I had EGR turned back on.
 

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Super Moderator
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7,479 Posts
I fine this hard to belive myself. Just got back with the bird on a road trip. Checked mileage 153 miles on 5 gallons = 30.6 !! This was flat ground cruise . 273 miles on 10 gallons =27.3 this was hills coming up I-81 in VA. How in the world ??? I still cant belive that. It was a steady cruise trip 75 MPH 2300 or so RPMs
Yeah, the 4.6 is awesome on the highway that way.
 

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Voice/Data Guru
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Wow Mike I have never heard of a V8 in our birds getting that. Jezz I sure was surprized to fine that math tells it like it is :)
 

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Must have had a nice tail wind along the way. :D

BTW, It's my last day at work here and I'm screwing off on the company computer on company time!!! :tongue:
 

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1,747 Posts
Engine: 4.6L SOHC
City MPG: 18
Highway MPG: 26
Fuel Used: 87/89
Average highway speed: 70-75mph
Average Climate: winter 20's, summer 80-90
Mechanical Mods: PI Intake
Mileage on the engine: 233K
Notes: High Flow cats, cold air intake
 

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Premium Member
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2,545 Posts
never heard of that kind of mileage? Dude my Tbird averaged about 32MPG going to TN. Did 2K RPM the whole way there. Windows cracked A/C off. V8's are very effecient while cruising. Thats just the way they are.
 

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159 Posts
Engine: 4.6L
City MPG: 19
Highway MPG: 23+
Average highway speed: Yup, set the Cruise for MPG, 55 mph- unless I'm intermittently 'in the radiator'...
Average Climate: Long Island-30s to 90s
Mechanical Mods: None
Milage on the engine: 90k
Comments: this is based on spec after the K&N Panel but BEFORE air delete and MAF cleaning... I'll see if it improves or not an update accordingly...
 

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12 Posts
Engine: 4.6

Combined mpg is right at 26. Thats a mix of city/highway,and a/c and non-a/c. I drive 82 miles round trip to work daily, and check the mileage often.
 

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741 Posts
Engine: 4.6L
City MPG: Unknown
Highway MPG: ~22
Combined MPG: ~15
Fuel Used: 93, usually from Citgo
Average Highway Cruise Speed: 70-75
Average Climate: Long Island weather - warm, mild humidity.
Mods: None.
Mileage on the Engine: 84,000
Comments: I kept track of how much gas I used over one summer and how many miles I drove and the average came out to be 15.07, I think. As of now, I get roughly 240 miles per tank before the warning light comes on. I've had a consistent CEL since I got the car in 2005, and as soon as I get something fixed, something else screws up. The current culprit is P0171/P0174. Cleaned the MAF, no dice. I haven't had the chance to look further into it, but I will when I go back home.
Update!

For my last two tanks, I used 89 octane.

Tank 1 averaged out to be 14.68 miles per gallon. Although this was with nearly bald and poorly inflated (see ~15 psi) tires.

For tank 2, I replaced the tires, but I had an issue with a misfiring cylinder. MPG for this tank turned out to be 14.72.

I do mostly around town driving, a little highway, but not much. I don't thrash on the car at all, so why my average gas mileage is so horrendous is beyond me.
 

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i'd say its probably the fact that one or more of your cylinders is misfiring and you have a broken torque converter.....that kind of deductive reasoning is not beyond me...lol
No no, I replaced the plugs/wires, that cleared up the misfire issue. And the TC isn't broken, it's just some minor shudder. Or moderate shudder, whatever.
 

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741 Posts
Oh no, I don't doubt that the TC is an issue, I fully believe it is. It's just not quite broken yet.

And I only limped around with a misfiring cylinder (#4, if it matters) for ~10 miles. So that second tank was a full tank, mixed highway/city, that got me a grand total of 14.72 mpg. Would a misfiring cylinder, even if only driven for 10 or so miles, or a shudder-y TC, really hurt fuel economy that badly?
 

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741 Posts
probably not the misfiring cylinder if it was only for 10miles, but a shuddery TC all the time is very detrimental to fuel economy
Well, that sucks. Mercon V flush and J-mod are in order, for sure. I didn't realize it would hit my fuel economy that badly. Hopefully I don't have to replace the TC yet.
 

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Newbie
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5,650 Posts
Engine: 4.6L
City MPG: 18
Highway MPG: 25
Combined MPG: 22
Fuel Used: 87 or 91 octane, depending on tune
Average Highway Cruise Speed: 75 MPH
Average Climate: 20* - 115* F, dry
Mods: See Sig
Mileage on the Engine: 1,500
Comments: Looking to get more highway MPG once I get the SCT PRP
 
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