Perhaps your MAF was affected by oil from the K&N filter. Have you checked that?

 

He replaced the paper air filter because he was getting bad gas mileage. I don't think the K&N is the culprit in this case.

For the original poster:
When you start the engine and let it run, do you smell anything from the exhaust? Does it smell like raw gas? What about after a 10+ mile drive? MPG is determined by the # of miles driven and the amount of gas consumed. The more idling you do, the worse your gas mileage (obvious stuff here). That means bad MPG can be the result of running excessively rich or excessively lean. Why lean? Because if the PCM sees an excessive amount of air (vacuum leak, air intake leak, etc...) it will compensate by adding more fuel to attain a 14.6:1 a/f ratio. I know this info doesn't help you one bit, but my Stang is also getting pretty horrible gas mileage.

The easiest way to check gas mileage is by doing a very long highway trip and filling up on gas right off the highway. When my Crown Vic was consistently getting 10 mpg local, I found it was getting 20 mpg on pure highway driving. That should at least tell you that the car isn't totally fubar'd and sucking down gas like there's no tomorrow.

 

Well I have "smelled" the exhaust and it does not smell like it is burning rich... as for the oil in the MAF... this problem was there before I replaced the air filter, that is why I originally replaced it, hopeing for an increase in MPG.

 

Does anyone else think his gas gauge might be on the fritz?

 

Man I hope that is what it is....I hate this! I hope they will actually be able to find something! Because last time I took it in, I mentioned the gas problem and they said it was normal to get to get around 15mpg.

 

As stated numerous times here, the gas gauge it useless anywhere in between full and empty. The only bonafide way to measure actual mileage is to fill the tank to the exact same level EVERY time and record the mileage driven and fuel used. Take it to the same station and use the same pump and follow a specific routine - i.e. insert the nozzle to a consistent depth and set it at the lowest flow rate. When it stops, pull it. If you don't do it exactly the same each time you'll skew your results. Regarding the dealer, you're going to need to log your usage religiously over a period of time in order to get them to dig into it (if there's not a glaring problem). Keep a log book and record all of your mileage and gallons pumped. You might even want to note the predominant driving for that tank, but that's not really relevant. Don't rely on the gauge and don't rely on the trip computer. It's a novelty at best.

 

The original poster said he filled up with about 15 gallons each time, that is a full tank, and then calculated mileage based on that. So he is doing it right. Something is wrong with the car if he can only manage 15mpg with conservative driving. I still would like to see a nearly exclusive highway trip with no traffic to see what it gets.

 

I have noticed in all of my new cars over the past 10 years that gas mileage was lower in the first couple of tanks of gas and several hundred miles. I attribute this to the process of "loosening up". This does include my '07 GT.

I mentioned the K&N because he said his stock air filter was replaced in a short timeframe.

 

I bought the car as a Dealer Demo car... already has 5K miles on it. The owner of the dealership drove it around for a couple months. So I know it is already broken in.

 

Same here, though I try and avoid traffic so I am averaging 17.6 city and 23 highway.

 

This is ****ing me off... I called my dealership to double check on my drop off for service tomorrow to fix this problem, and they said there is nothing they can do to fix any associated MPG problem unless there is a check engine light on. I called the other two main dealerships in Tampa, and they both said the same thing! !!!!! The most I have ever gotten in 200Miles on a single tank.

 

Since the gas tank has a 16 gal capacity, I'd imagine that 200 miles on 15 gal is roughly 13 mpg, which isn't too bad and expected for stop and go driving. However, this is a problem if it was driven on 100% highway roads.

Things to check:
tire pressure - is it at least 32 psi?
fuel filter - might as well change it out.
Engine oil - how old is it? Make sure to use 5W-20.
gas - find a Top Tier station (Shell, Chevron) or use quality gas (Usually Sunoco has good stuff) Avoid BP, I can never get good gas mileage using their gas. Use 87 octane!
e-brake - check to see if the rear brakes are dragging on the rotors. usually a frozen e-brake can cause this.

Next time, run a bottle of Chevron Techron cleaner when your gas tank runs low. Then fill up with fresh 87 octane gas.

 

200 is the most I have gotten... have gotten anywhere from 170-200 miles/tank.

Tire pressure- 32psi all around
Fuel filter - only 5000miles on it
Engine Oil - What ever Ford puts in it.
Gas- I usually use Sunoco 93oct. Is there a reason to use 87 instead? Will this help?
e-brake- Has not been used since before I got it...it's an Automatic not a Manual, live on pretty flat terrain.
And shouldn't I not run the Techron through until I am about to get an oil change?

 

Here's some light reading for you to look at:

http://www.repairfaq.org/filipg/AUTO...l#GASOLINE_001

 

When was the last time the engine oil was changed? How much oil is in there? What filter are you using? 5000 miles means it should have had the oil changed at least once.

87 octane gas usually gives you the best gas mileage since that is what the car was designed to use.
Some cars get better gas mileage on 93, but I see zero reason to use 93 octane unless you are pushing a LOT of timing.

Check your rear rotors for signs of overheating brakes (dragging e-brake caused by freezing inside the cables). I always use my e-brake whether it is an automatic or manual. I do not trust the puny parking pawl to hold nearly 2 tons of steel mounted on low-friction rollers.

You can use the Techron in the gas tank whenever you want.
It usually solves a lot of detonation problems, so it is worth a try.

 

Perhaps it's a fuel filter problem as someone had touched on earlier. I remember when I had my Cavalier, I had problems with my car "cutting off" from time to time when I was driving and my fuel gauge being terribly inaccurate. I also got crappy gas mileage for what was suppose to be an economy car. Took it to one of the repair shops I trust and found that debris (presumably from the pump nozzle) got in to the tank and contaminated it giving me all sorts of problems. So long story short, even if the car is only 5,000 miles old, still wouldn't hurt to have the fuel filter (or tank in general) looked at.

 

I don't have an answer to your problem, but I do have an observation regarding my own MPG. I have an 05 GT, automatic. I do not drive conservatively. I keep a record of each fill up. In 22 months I've filled up 73 times. If I average all 73 comp. MPG it comes to 19.94. I also calculate it myself using the odometer because of a glitch in my tripmeter.(it will sometimes reset itself within 5 miles) My MPG average over 73 fill ups is 19.54.
My son lives 135 miles away. I filled up and drove all highway and beltway. I checked the comp. before exiting the highway and it was showing over 27 MPG. All highway, but 65,75 sometimes 85 MPH (when passing). I filled up a day or so after I arrived. On that new tank I had a lot of short, quick trips. No real traffic, just slow driving with a lot of traffic lights. Out of curiosity, I checked the comp. MPG before heading home and I was getting 12 MPG! ( I don't live in a city and wanted to know what she would get) I drove home on that same tank and as I arrived home, I checked again and she was getting 22MPG. I think these ponies hate to trot and love to run. I hope you find an answer to your problem.Sorry for the long post.

 

If you are using 93 with a stock tune your mileage will suck use 87

 

Bingo!

 

The octane rating shows much more resistant the gas is towards detonation/knock. In other words, a higher octane will burn "slower" than a lower octane gas. 87 octane burns faster than 93 octane gas, hence it will tend to burn "cleaner" and help you pass emissions inspection. Never try to pass CA/NJ emissions while running 93 octane. You may get by, but why waste the money? The cars that require 91 octane generally have knock sensors to help them run 87 octane gas.