Poor gas mileage

I'm getting really poor gas mileage off my 2008 4.0. We're talking like 15 MPG. I know I drive like an ass, and that might be why my MPG look like this, but I just wanted to reach out to see if there could be something else effecting my mileage aside from my driving style. Any suggestions? Thanks!

I just assumed they were never really that fuel efficient considering it's a 4.0L Single Cam motor. I could be wrong, but that's the impression I've always had.

I avg. about 20 mpg in my Coyote but for 38 min. of a 40 min. commute is 55 mph+.

I've always heard the 4.0 was a pig and meh gas milage. But never any first hand experience with it.

Other than my friend that said he got high 20's and it was fast enough to be a GT killer. Ha

Wes06 said:

I've always heard the 4.0 was a pig and meh gas milage. But never any first hand experience with it.

Other than my friend that said he got high 20's and it was fast enough to be a GT killer. Ha

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lol

I picked up an 05 for my daughter and I'm convinced it gets worse mileage than my 650whp Shelby.

She only drives a short stop and go to school daily that doesn't help, but it's ridiculous. I plan to send her to college in the wife's Honda and unload the V6 Mustang after high school.

If you buy a mustang u shouldn't be worried about fuel economy just saying

07TR said:

If you buy a mustang u shouldn't be worried about fuel economy just saying

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There's always that, too.

My 05 GT full bolt ons and hotrods gets average 12mpg I think, most of my driving is around town but even highway is maybe like 16, I know 4.10s will affect it but I've always thought something was off in my tune and plan to get a wideband for Lito this year. Maybe it's normal?

KatoS197 said:

There's always that, too.

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Exactly...

Low 20 to 23mpg on the highway in my 05 GT. Average 14 to 16 in town with lots of lights and crosswalks with speed limit at 25mph. Long trips I can pull around 24 to 25mpg on interstate.

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My son's '05 4.0 has been getting 20.3 mpg (on-board and hand calculated are the same) in mixed driving conditions. Mostly urban driving on 35 to 45 mph posted roads with stop signs/traffic lights mixed in and shortish trips of 30 minutes or less. It has a mild tune for a CAI and dual exhaust.

I get between 19 and 20 in mixed driving. 10 miles of freeway, and then about 10 minutes of country roads with multiple stop signs. It's a relative gas hog compared to the new V6 (as it should be as a 2v SOHC).

Few things I can suggest. I'm still kinda new to cars, so some more experienced guys might say otherwise, but here's what I would do

New plugs, or at least check that the plugs are properly gapped (also optional to replace wires and distributor)
Clean the Throttlebody very well
New engine air filter
Can try seafoam
Get a tuner or CAI with a more economical or revised tune?

I drive like my foots glued to the gas pedal and I still get 18-19 avg in an urban area with some highway driving. I have a bama 93 race tune, dual exhaust, new plugs, cleaned my TB, airaid CAI.

My 05 saw 17 on average. It was a V6 car. I am also convinced here in South Florida our roads are a HUGE factor in Gas Mileage. Our roads are made up of concrete and ground up corral. Add in the excessive Heat we deal with and you are driving on sandpaper. Very abrasive on tires and ultimately hurts fuel economy

05 v6 convertible (4.0 engine) gets 20-24,depending on road. Love it! I use at least 89 octane and have a performance/mileage chip installed. don-ohio ^)

The biggie is how you drive the car. But also, good plugs and a clean air filter are a must, too.
With my v6's, I've always made over 20mpg, and usually in the mid-20's on the highway. Yeah, driving like an idiot, like flooring it from a stop every time, will kill mileage.

Update to my post about getting 16mph if that, changed from ford racing shorties yesterday and a new magnaflow h pipe to pacesetter long tubes and catted h and picked up 10mpg on my way home, I'm not sure how it's running without an updated tune but cant explain the increase unless it was the fuel filter (old one was only about a year old as well)

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You replaced the fuel filter as well? Seems to me like that would account for your pickup in mpg, granted i'm no mechanic but I can't imagine why headers would affect mpg that much especially if theyre a quality brand.