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Bad MPG!

Old 11-12-2018, 10:03 AM
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NamTDuong
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Bad MPG!

Hello all,

I have a 2013 Convertible base with no aftermarket modifications. I am not an erratic driver and do not race my G37. The current issue is that the MPG counter show averages of lower than 10MPG. I had reset the counter but it still shows the low average. I would appreciate any advice. Thank you!

Last edited by NamTDuong; 11-12-2018 at 10:04 AM. Reason: Picture attachment not popping up
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Old 11-12-2018, 10:11 AM
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Bostonreefer
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Do A Real world test and see what your getting Xgal / miles driven .... This will at least eliminate if the computer is off or if there is really something mechanically bringing your MPG down that much...
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NamTDuong (12-26-2018)
Old 11-12-2018, 10:18 AM
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NamTDuong
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Thank you for replying.

How would I approach the real world testing? The only available MPG counter I know of is the one in the dash.
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Old 11-12-2018, 11:38 AM
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Hashim
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what mileage are you at? have you changed tires? whats your maintenance schedule like? any obd2 codes showing after a scan? how long have you had the car? it always had bad mileage or has it recently changed?
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NamTDuong (12-26-2018)
Old 11-12-2018, 11:44 AM
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  • Get the miles traveled from the trip odometer
  • Divide the miles traveled by the amount of gallons it took to refill the tank. The result will be your car's average miles per gallon yield for that driving period.
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NamTDuong (11-13-2018)
Old 11-12-2018, 11:49 AM
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NamTDuong
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-Current mileage is at 7.9.
-The two front tires are due for a change, 4 month old tires in rear.
-Oil change performed on 10/24.
-Check engine light popped on Friday, vehicle is due to go through diagnosis today at Infiniti dealership.I have had the car for over 2 years, bought it pre-owned. Out of warranty.

Bostonreefer:

If the infiniti dealer does not find the issue, I will perform the test. Thank you for your expertise.
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Old 11-12-2018, 12:14 PM
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projectpanda13
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The car's mpg calculator is pretty accurate to what my manual calculations are. I start with a full tank, reset my odometer, drive at least half tank (I usually pump gas at 1/4 tank mark), pump a full tank, I'll take my miles driven (ex. 380 miles) and divide the miles by the amount of gallons to get back to full. ex: 380 miles / 16 gallons ~ 23.75 mpg.

I normally average 22 mpg mixed driving (about 80 mph on the interstate, and sitting in traffic for about 1 hr. I have a 120 daily commute to work and then back home.)

What's crazy is, I just got my tune yesterday and my dash reading said 32 mpg. I'm going to check if that's true as I run down the tank in the next couple of days.

Latez
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NamTDuong (11-13-2018)
Old 11-12-2018, 02:11 PM
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Hashim
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Originally Posted by NamTDuong View Post
-Current mileage is at 7.9.
-The two front tires are due for a change, 4 month old tires in rear.
-Oil change performed on 10/24.
-Check engine light popped on Friday, vehicle is due to go through diagnosis today at Infiniti dealership.I have had the car for over 2 years, bought it pre-owned. Out of warranty.

Bostonreefer:

If the infiniti dealer does not find the issue, I will perform the test. Thank you for your expertise.
I don't understand what you mean by mileage is 7.9

what kind of tires did you put on? tires and tire pressure affect mileage as well, some tires give better mileage than others, have you checked your tire pressure...

is the mpg change recent?, i.e. did it start around the time you got the CEL?

It could be so many things depending on your answers it would help a lot to narrow them down.

If its been a recent change and you're getting an CEL it could be related to a sensor (MAS or 02) or something else emissions related like your cats, but if your mileage is high you might benefit from changing your spark plugs depending on what you past maintenance schedule has been(Not just oil changes but other maintenance, i.e. have you changed your air filters recently.) this may be true at a lower mileage too.


You can probably get the CEL code scanned for free at an autoparts store, but the dealershould offer a solution after scanning it as well
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NamTDuong (11-13-2018)
Old 11-12-2018, 02:18 PM
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John Hannon
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Iíve got an app on my phone, input your mileage since the last fill up and fuel used and bingo.
As others have said the onboard computer is pretty accurate
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Old 11-12-2018, 07:56 PM
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slartibartfast
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Call me old-fashioned but I would not rely on the computer for mpg. Use the manual method above for true mpg. It's not at all difficult.
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Old 11-13-2018, 05:55 AM
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John Hannon
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Here are the figures for my 2011 automatic convertible, this is UK gallons.
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Old 11-13-2018, 01:38 PM
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Jsolo
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UK gals == imperial gallons? (1 imp gal = 1.2 US gal).
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Old 12-26-2018, 06:09 PM
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7.9 is pretty terrible I was averaging 15 and i only kept my foot planted to the ground everywhere I went. I would check your tire pressures as that might help if they are lower then what is factory recommended
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Old 12-26-2018, 09:26 PM
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NamTDuong
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Hello Everyone,

An update on the situation:

-Currently average 15.5 MPG in the city of Chicago, IL., some highway
-Firestone Firehawk Indy 500s around all 4 a month old
-Berks HFC
-TopSpeed Pro 1 Exhaust
-Stillen CAI
-No tune or other mods
-No codes, TPMS, or other dash lights.
-Only use Shell V-Power Gasoline

Would that be about the correct MPG that it would be at?
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Old 12-26-2018, 10:28 PM
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Stop and go kills fuel mileage. Winter blend fuel hurts fuel mileage. Cold weather hurts fuel mileage. If you warm your car up that hurts fuel mileage.
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