Poor gas mileage

[Ragtop]

2007 GT Convertible 4.6l. So I recently bought this with 92k. Car is a well cared for single owner car. However this thing says 9.5 average mpg . Supposed to get between 16-20 depending how you drive. looks like a new(er) TB. Has the # 81 on the butterfly both sides facing air filter. What is that telling me? Runs great, no unwanted noise. Runs really smooth tho. Has a modified air intake and SLP muffler delete dual exhaust. At 63 I just want a nice hotrod type car with good gas mileage 16-20mpg which is why I bought this. Any suggestions are appreciated. Be it known I have a really hard time trying to post messages and answering back. Cant seem to figure how to navigate this forum, So thank you in advance for any help. If I dont answer you know why.

 

[Dino Dino Bambino]

Since your engine runs well, I'd wager that your upstream O2 sensors will need replacing but have the ECU scanned for fault codes to find out why the engine's running rich.
You can also use an ELM327 OBD2 Bluetooth scanner and monitor live data using the Car Scanner app on your smartphone. This will show if the O2 sensors are working properly and show short term/long term fuel trims.

 

[stkjock]

have you manually calculated the MPG? reset the trip computer to verify you're getting a correct reading?

 

[86GT351]

2007 GT Convertible 4.6l. So I recently bought this with 92k. Car is a well cared for single owner car. However this thing says 9.5 average mpg . Supposed to get between 16-20 depending how you drive. looks like a new(er) TB. Has the # 81 on the butterfly both sides facing air filter. What is that telling me? Runs great, no unwanted noise. Runs really smooth tho. Has a modified air intake and SLP muffler delete dual exhaust. At 63 I just want a nice hotrod type car with good gas mileage 16-20mpg which is why I bought this. Any suggestions are appreciated. Be it known I have a really hard time trying to post messages and answering back. Cant seem to figure how to navigate this forum, So thank you in advance for any help. If I dont answer you know why.

Have you reset the paprmeters? Every time you get gasoline they should be reste. They are nothin gmore than an average. The only proper way to tell is keep a log of How many miles you drove with how many gallons you put in.

 

[Pentalab]

U won't get 20 mpg around town, not a chance.
Fill gas tank to max.
Set trip meter to zero.
Drive till u are down to a 1/4 tank.
Fill tank up to FULL.
Note how many gallons u put in...and what the trip meter says. Then do the math calcs.


The online mileage indicator built into the car is a real slow rolling average.

Around town I get 20 litres per 100 km = 11.76 miles per US gallon

 

[MasterofDisaster]

Have you reset the paprmeters? Every time you get gasoline they should be reste. They are nothin gmore than an average. The only proper way to tell is keep a log of How many miles you drove with how many gallons you put in.

Agreed. My 08 routinely tells me I'm getting 1.5mpg more than reality.

 

[86GT351]

Agreed. My 08 routinely tells me I'm getting 1.5mpg more than reality.

This has never changed. It is just averages. If it is not reset then you are not getting factual info.

 

[07 Boss]

I reset mine about every 3 or 4 tanks, That will give you enough driving under different conditions to get a decent reading. I have also reset it coasting downhill at speed and have gotten 99.9 mpg on it.

 

[Juice]

Useless gadget. I go by low fuel light. Full tank, reset trip odo. I know my vehicles, and the light always comes on within a few miles. Dont even calculate mpg anymore, and I know I have a good 30+ miles fuel left after the light. Guess its from riding as most bikes only have a low fuel light lol

 

[GriffX]

CMDP cost me 1 mpg in city, at least. And tune can have an effect too.