Gas Mileage has Crashed!
02-26-2016, 08:02 PM
#1
Gas Mileage has Crashed!
The city driving gas mileage for my 2011 base (16,000 miles) has dropped from around 19 to less than 12 MPG. The only changes to my car have been the installation of an OEM Nav, a Heads Up unit, and a M2W switch (which for the most part has been kept in mild mode).
The plan is to get it to my mechanic and run a diagnostic on it, but for now, any thoughts/ideas as to the nature of the problem?
The plan is to get it to my mechanic and run a diagnostic on it, but for now, any thoughts/ideas as to the nature of the problem?
02-26-2016, 08:30 PM
#3
Burning Brakes
The city driving gas mileage for my 2011 base (16,000 miles) has dropped from around 19 to less than 12 MPG. The only changes to my car have been the installation of an OEM Nav, a Heads Up unit, and a M2W switch (which for the most part has been kept in mild mode).
The plan is to get it to my mechanic and run a diagnostic on it, but for now, any thoughts/ideas as to the nature of the problem?
The plan is to get it to my mechanic and run a diagnostic on it, but for now, any thoughts/ideas as to the nature of the problem?
02-27-2016, 12:27 AM
#5
Le Mans Master
The immediate questions that come up are: 1. How many tankfuls have you gone through that duplicated the low mileage level? 2. Are you figuring it out yourself based on actual usage, or are you using the DIC (vehicle computer)?
02-27-2016, 07:18 AM
#7
Team Owner
iF YOU NEVER HIT THE HIGHWAY,IT IS NORMAL FOR YOUR GAS MILEAGE to decrease big time. Take her for a run on the highway a few times and see if that helps.
02-27-2016, 08:50 AM
#9
Team Owner
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First, how accurate are your mpg calculations? If you are not tracking factual mpg, don't go to guns yet. Some people think that reading the gas gauge constitutes mpg. Not.
Second, how many tank ups had 19 mpg, and how many tankfuls registered 12 mpg? A single fill up with a gas nozzle back pressure regulator set too low will result in a one time significant delta.
No need to panic until you have more data!!!!!!! LOL
Second, how many tank ups had 19 mpg, and how many tankfuls registered 12 mpg? A single fill up with a gas nozzle back pressure regulator set too low will result in a one time significant delta.
No need to panic until you have more data!!!!!!! LOL
02-27-2016, 09:13 AM
#10
Le Mans Master
That is a big drop.
OP we need more info.
Is your driving route, stop lights, gear selection all the same?
Any codes?
Confirm how you measure MPG.
Brake drag, stuck injector, fuel leak are all possibilities.
Let us know and good luck.
OP we need more info.
Is your driving route, stop lights, gear selection all the same?
Any codes?
Confirm how you measure MPG.
Brake drag, stuck injector, fuel leak are all possibilities.
Let us know and good luck.
02-27-2016, 09:14 AM
#11
Drifting
Member Since: Jul 2011
Location: Boca Raton Florida
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19 in town? Neve got that in entire 5 years. 12 is my average combined, sometimes even 9 , but i know why that is. It looks like you need to have a heart to heart with your right foot. Mine has full permission to do whatever it wants, that was our accord when i bought my 11 MN6 GS. NPPS open all night the time, it is a music to my ears having this car roar, pop and crackle. Heck with the gas milage, that is the price of all that fun.
Having said that i appreciate your concern, a radical change in something requires an investigation.
Having said that i appreciate your concern, a radical change in something requires an investigation.
02-27-2016, 09:23 AM
#12
Drifting
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Oh, on the very outside case, if you have teenagers at the driving age ( especially boys) i would hide my fob very well. When i was 15 ish, it took my dad more than a year to figure out why he was filling so often, did not know that i had 5 sets of spare keys made for his car and went for crazy joy rides after everyone fell a sleep. 
02-27-2016, 09:36 AM
#13
Safety Car
Oh, on the very outside case, if you have teenagers at the driving age ( especially boys) i would hide my fob very well. When i was 15 ish, it took my dad more than a year to figure out why he was filling so often, did not know that i had 5 sets of spare keys made for his car and went for crazy joy rides after everyone fell a sleep.
02-28-2016, 08:14 PM
#15
Thanks for all the input. My first (and obvious) step will be to recalculate the MPG the old fashioned way. I am also going to pull the air filter to ensure it is not clogged up by something. Same for checking the tire pressure, but don't see how it could drop the mileage by 33%.
As to the brakes, the car rolls freely in neutral. And at idle I am not experiencing any roughness. O2 sensor makes some sense, but I'm not getting a check engine light (checked to see if the light was indeed working).
Will repost once I have more info.
As to the brakes, the car rolls freely in neutral. And at idle I am not experiencing any roughness. O2 sensor makes some sense, but I'm not getting a check engine light (checked to see if the light was indeed working).
Will repost once I have more info.
03-01-2016, 12:13 AM
#18
Le Mans Master
Almost none of the things others have advised (tires, air filter, winter blend of fuel-which would have occurred in Oct/Nov.=etc.) would cause your mileage to go from 19 to 12.
You now have said you are going to "recalculate the MPG the old fashioned way". That should have been the first thing you did before posting. Also, you didn't answer my question as to how many tank fillups have you gone through with it getting 12 MPG. A single tank of bad mileage seldom means anything. My bet is that you will find there is either a calculation problem in your computer, a mental error regarding a change in driving style by you, or simply a blip for reasons you cannot determine.
Is there any possibility that your previous "19 MPG" was a mere estimate which you thought was correct, or that your current 12 MPG could be the same thing? Also, you might reconsider whether your 19MPG in the "city" is a true city, stop-and-go setting, or is it a city commute with lots of consistent highway speed miles? That is a really high figure for metropolitan city driving.
If you want to accurately check your mileage in the future, try the following: Always fill up at the same station, preferably at the same pump. ALWAYS hand-calculate using exact miles driven and exact fuel used. Never try to calculate after traveling a relatively short distance.
Hope it works out for you....
You now have said you are going to "recalculate the MPG the old fashioned way". That should have been the first thing you did before posting. Also, you didn't answer my question as to how many tank fillups have you gone through with it getting 12 MPG. A single tank of bad mileage seldom means anything. My bet is that you will find there is either a calculation problem in your computer, a mental error regarding a change in driving style by you, or simply a blip for reasons you cannot determine.
Is there any possibility that your previous "19 MPG" was a mere estimate which you thought was correct, or that your current 12 MPG could be the same thing? Also, you might reconsider whether your 19MPG in the "city" is a true city, stop-and-go setting, or is it a city commute with lots of consistent highway speed miles? That is a really high figure for metropolitan city driving.
If you want to accurately check your mileage in the future, try the following: Always fill up at the same station, preferably at the same pump. ALWAYS hand-calculate using exact miles driven and exact fuel used. Never try to calculate after traveling a relatively short distance.
Hope it works out for you....
Last edited by buckmeister2; 03-01-2016 at 12:22 AM.
03-01-2016, 12:25 AM
#19
Team Owner
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Almost none of the things others have advised (tires, air filter, winter blend of fuel-which would have occurred in Oct/Nov.=etc.) would cause your mileage to crash like it has.
You now have said you are going to "recalculate the MPG the old fashioned way". That should have been the first thing you did before posting. Also, you didn't answer my question as to how many tank fillups have you gone through with it getting 12 MPG. A single tank of bad mileage seldom means anything. My bet is that you will find there is either a calculation problem in your computer, a mental error regarding a change in driving style by you, or simply a blip for reasons you cannot determine.
If you want to accurately check your mileage in the future, try the following: Always fill up at the same station, preferably at the same pump. ALWAYS hand-calculate using exact miles driven and exact fuel used. Never try to calculate after traveling a relatively short distance.
Hope it works out for you....
You now have said you are going to "recalculate the MPG the old fashioned way". That should have been the first thing you did before posting. Also, you didn't answer my question as to how many tank fillups have you gone through with it getting 12 MPG. A single tank of bad mileage seldom means anything. My bet is that you will find there is either a calculation problem in your computer, a mental error regarding a change in driving style by you, or simply a blip for reasons you cannot determine.
If you want to accurately check your mileage in the future, try the following: Always fill up at the same station, preferably at the same pump. ALWAYS hand-calculate using exact miles driven and exact fuel used. Never try to calculate after traveling a relatively short distance.
Hope it works out for you....
If you want to be even more **** about it, you can go through several tanks, keeping track of the total gallons and total miles traveled with those tanks.
