Gas mileage in 2009 LX getting way worse this past year - Honda Civic Forum



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Old 12-21-2016   #1
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Gas mileage in 2009 LX getting way worse this past year

Hi folks,

So, I've done a search on this topic and have read several similar threads. No one seems to either posted a resolution or made any headway into it. But, I may as well post mine since this seems to be an actual problem.

I'm the original owner of an 09 LX Civic AT. It has about 90k miles on it. I've done all of the maintenance and maintenance scheduled items, but regardless, in the past year, my fuel economy has just fallen off a cliff.

I do fuel economy calculations by using my trip odometer and fuel pump readings nearly every time. I used to get around 42 mpg HWY (we take a lot of road trips), and for mix HWY and city driving, I would average about 38 mpg. My driving patterns have NOT changed, and neither has the weather (we live in California, and temps on the coast never got hot nor cold) changed, our altitude, nor gas mix (always E10 out here). But, our mileage has gone from about 38 mpg (on average) down to barely 31 mpg.

The tires have full pressure, I've done tire alignment a year and a half ago. I haven't done spark plugs or cables yet. I just did fuel injector cleaner so I'll see how that goes. Other than that, I can't figure out how this car is eating so much gas lately. It also feels like I'm losing power too. Before, it felt much more torquey and got onto the on ramps with gusto. Nowadays, it kinda feels a bit underpowered.

Any ideas? I figured I would try out this place before getting it a look over by a mechanic.
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Old 12-21-2016   #2
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Re: Gas mileage in 2009 LX getting way worse this past year

Did this problem begin after replacing a set of tires?



Check for codes?
Got a scanner? Will it display live operating data from the PCM?
I'd be interested in fuel trims, MAF values, and AF sensor responses.
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Old 12-22-2016   #3
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Re: Gas mileage in 2009 LX getting way worse this past year

Nope. In fact, I was wary of that since I put on Michelin Defenders. They are LRR tires, but I figured they would impact gas economy. They only slightly di at the time, and we were getting around the same mileage as before.

It seems this degradation of fuel economy is quite common with Honda Civics. I see a lot of threads on here with a search that has people asking the same thing. In fact, several years ago, I posted the same thing about my 01 Honda Civic. I'm the original owner of that one too. I used to get 44 mpg HWY, and that just went to **** around 120k miles. I figured it was the drive train, since it used to drive 65 mph at around 2k rpm. But, after my tranny started flaring, I need to be at 2.5k rpm to get to 65 mph. Could be a red herring though. On that car, I've done it all: spark plugs, O2 sensor (on the engine block), AT tranny fluid with Honda ATF, brakes, etc... I've taken every suggestion on here to fix the fuel economy problem but it's still hosed. At best, I was getting around 38 mpg HWY on the car after that. I just decided to live with it since that was the most commonly reported mileage. However, the car's mileage has also gotten worse since then and can barely do 35 mpg HWY. I'm running fuel injector cleaner in that one too to see if it helps. I'll report later.

I might need to do another tune up. Maybe there's a fuel leak somewhere. I dunno. The fuel economy on both cars have gone to **** over the years. It makes me wonder if this problem is systemic or relegated to Honda Civics.
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Old 12-25-2016   #4
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Re: Gas mileage in 2009 LX getting way worse this past year

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Originally Posted by mililani View Post
Nope. In fact, I was wary of that since I put on Michelin Defenders. They are LRR tires, but I figured they would impact gas economy. They only slightly di at the time, and we were getting around the same mileage as before.

It seems this degradation of fuel economy is quite common with Honda Civics. I see a lot of threads on here with a search that has people asking the same thing. In fact, several years ago, I posted the same thing about my 01 Honda Civic. I'm the original owner of that one too. I used to get 44 mpg HWY, and that just went to **** around 120k miles. I figured it was the drive train, since it used to drive 65 mph at around 2k rpm. But, after my tranny started flaring, I need to be at 2.5k rpm to get to 65 mph. Could be a red herring though. On that car, I've done it all: spark plugs, O2 sensor (on the engine block), AT tranny fluid with Honda ATF, brakes, etc... I've taken every suggestion on here to fix the fuel economy problem but it's still hosed. At best, I was getting around 38 mpg HWY on the car after that. I just decided to live with it since that was the most commonly reported mileage. However, the car's mileage has also gotten worse since then and can barely do 35 mpg HWY. I'm running fuel injector cleaner in that one too to see if it helps. I'll report later.

I might need to do another tune up. Maybe there's a fuel leak somewhere. I dunno. The fuel economy on both cars have gone to **** over the years. It makes me wonder if this problem is systemic or relegated to Honda Civics.

Quick question, with 120+k, what do you think the whole drive train still functions like a new car?

Getting 44 mpg, your lucky. The most I ever got from my 2012 HF was 43...with the cruise control on.. after that, I usually get 37 / 38 and don't expect much more. ... there's more to in life than to worry about not getting 44 mpg after 120k on the car. Just my .02 cents..good luck
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Old 12-31-2016   #5
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Re: Gas mileage in 2009 LX getting way worse this past year

Milliani You may need a induction cleaning ...
i would 1st start by running a strong concentrated fuel cleaner
in the tank like "BG 44k" pour it in on a full tank of gas. its the strongest
pour in the tank fuel system cleaner too use. and see if that makes a difference ...?
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Old 12-31-2016   #6
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Thumbs up Re: Gas mileage in 2009 LX getting way worse this past year

braggs i tried a can of 44k in my car and i gained better gas econo
and alot better pep.!! power stuff realy do work milani give it shot
braggs you told me about the moa last time its what i use in my si
fogot to thank you. ! cheers to all have a happy new year!!
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Old 12-31-2016   #7
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Re: Gas mileage in 2009 LX getting way worse this past year

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braggs i tried a can of 44k in my car and i gained better gas econo
and alot better pep.!! power stuff realy do work milani give it shot
braggs you told me about the moa last time its what i use in my si
fogot to thank you. ! cheers to all have a happy new year!!

glad to hear You tried it and Got great results. say are You still modifying
Your 91 Civic Si ? if so... post up some Pics for us to see will yah...?

Happy New Year... cheers
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Old 12-31-2016   #8
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Re: Gas mileage in 2009 LX getting way worse this past year

my guess is just engine losing compression overtime, just wear.
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Old 01-08-2017   #9
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Re: Gas mileage in 2009 LX getting way worse this past year

Ok, folks. Much thanks for all of the responses. I just wanted to do an update. So, I ran a full 20 oz of Chevron 65740 Techron Concentrate Plus Fuel System Cleaner in both Civics. I think it helped. I just checked fuel mileage on the 01 Civic after a fuel tank of gas and doing about 90/10% hwy/city driving. I got around 39 mpg. I think straight hwy mileage would be closer to 42 mpg. I will be doing a long drive from central, CA to San Diego in Feb, so I'll be checking to see what my straight HWY gas mileage will be soon enough. I'm not expecting 44 mpg like the 01 civic used to get. But, if it's near 42, I'll be happy.

As for the 09 Civic, my wife just did a long drive to Napa Valley straight HWY miles. She got 39 mpg, which isn't that far off the 42 mpg we used to get--and this was confirmed by us every time we used to drive to L.A. (which was almost every other week). However, on the return trip, she averaged just 35 mpg. Although, 10% of the drive was a mix of city driving and some stop and go traffic on the free way. But, it's not far off the 38 mpg we used to get with mixed driving.

Anyways, I've got another set of Techron. There was a huge sale and rebate on it, so I bought another set. Should I try that BG 44k out still or just do another Techron? Also, I'm thinking about doing her spark plugs. Her car seems like it has lost a bit of power and pep from a stop. I'll let you guys know how that goes.
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Old 01-08-2017   #10
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Re: Gas mileage in 2009 LX getting way worse this past year

Quote:
Originally Posted by ezone View Post
Did this problem begin after replacing a set of tires?



Check for codes?
Got a scanner? Will it display live operating data from the PCM?
I'd be interested in fuel trims, MAF values, and AF sensor responses.
BTW, sorry I didn't see the bottom part. I do have an ODB 2 scanner. So far, I've only used it to determine my CEL codes on the 01 civic. Once I resolved that issue (1 code was due to a worn out fuel tank cap, and the other was due to a worn out coolant thermostat -- both easy fixes). Someone else on another forum mentioned fuel trims. I'm going to see if my ODB 2 software is able to get the data. Anything I should specifically look for?
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Old 01-08-2017   #11
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Re: Gas mileage in 2009 LX getting way worse this past year

Quote:
Originally Posted by mililani View Post
Ok, folks. Much thanks for all of the responses. I just wanted to do an update. So, I ran a full 20 oz of Chevron 65740 Techron Concentrate Plus Fuel System Cleaner in both Civics. I think it helped. I just checked fuel mileage on the 01 Civic after a fuel tank of gas and doing about 90/10% hwy/city driving. I got around 39 mpg. I think straight hwy mileage would be closer to 42 mpg. I will be doing a long drive from central, CA to San Diego in Feb, so I'll be checking to see what my straight HWY gas mileage will be soon enough. I'm not expecting 44 mpg like the 01 civic used to get. But, if it's near 42, I'll be happy.

As for the 09 Civic, my wife just did a long drive to Napa Valley straight HWY miles. She got 39 mpg, which isn't that far off the 42 mpg we used to get--and this was confirmed by us every time we used to drive to L.A. (which was almost every other week). However, on the return trip, she averaged just 35 mpg. Although, 10% of the drive was a mix of city driving and some stop and go traffic on the free way. But, it's not far off the 38 mpg we used to get with mixed driving.

Anyways, I've got another set of Techron. There was a huge sale and rebate on it, so I bought another set. Should I try that BG 44k out still or just do another Techron? Also, I'm thinking about doing her spark plugs. Her car seems like it has lost a bit of power and pep from a stop. I'll let you guys know how that goes.

i had luck with bg 44k got mine of ebay cheap works great.!
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Old 02-21-2017   #12
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Re: Gas mileage in 2009 LX getting way worse this past year

Quote:
Originally Posted by mililani View Post
Ok, folks. Much thanks for all of the responses. I just wanted to do an update. So, I ran a full 20 oz of Chevron 65740 Techron Concentrate Plus Fuel System Cleaner in both Civics. I think it helped. I just checked fuel mileage on the 01 Civic after a fuel tank of gas and doing about 90/10% hwy/city driving. I got around 39 mpg. I think straight hwy mileage would be closer to 42 mpg. I will be doing a long drive from central, CA to San Diego in Feb, so I'll be checking to see what my straight HWY gas mileage will be soon enough. I'm not expecting 44 mpg like the 01 civic used to get. But, if it's near 42, I'll be happy.

As for the 09 Civic, my wife just did a long drive to Napa Valley straight HWY miles. She got 39 mpg, which isn't that far off the 42 mpg we used to get--and this was confirmed by us every time we used to drive to L.A. (which was almost every other week). However, on the return trip, she averaged just 35 mpg. Although, 10% of the drive was a mix of city driving and some stop and go traffic on the free way. But, it's not far off the 38 mpg we used to get with mixed driving.

Anyways, I've got another set of Techron. There was a huge sale and rebate on it, so I bought another set. Should I try that BG 44k out still or just do another Techron? Also, I'm thinking about doing her spark plugs. Her car seems like it has lost a bit of power and pep from a stop. I'll let you guys know how that goes.


Hey Mililani i know its been awhile since Your last posting but did You ever

clean Your (Mass Air Flow Sensor...?) reason for asking is theres no mention

of it in Your postings...? "that's a DYR' maintenance thing to do" if it hasn't

been done in a long while you could probably pick-up slightly better fuel

economy by just spray cleaning it let dry put it back in...? Just my 2 cents.
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