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Changes in gas mileage after 50k miles

Created May 19, 2009, at 1:55 am by sc1641

I bought a 2007 HCH in April of 2007. I will have to say I LOVE this car... It is AWESOME! I have noticed though that every since I turned about 50,000 miles my gas mileage has gone way down. I was getting on average between 40 & 42 MPG but and now getting between 32 & 35 MPG. I have not changed my driving habbits or where I drive to. I am thinking the fuel filter might need to be changed but was wondering if anyone else was having the same issue.

I am only looking for helpful productive responses. I love my Civic and don't want to hear about how upset you are about yours!

Thanks for responding

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Mendel Leisk
Senior Member

2 years ago

We currently have an 06 Civic Hybrid, but the first thing that comes to mind is the Oxygen sensor, which I believe was the culprit for declining mileage in a previous Accord we had. That said, it could be a myriad of things. A few ideas:

1. change of tires, to some with higher rolling resistance.

2. oil change with higher viscosity (or overfilled)

3. brakes dragging

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MSantos
Senior Member

2 years ago

HI SC;

Like Mendel said, there are quite a few things we can think of, but the three that Mendel mentioned are the most common.

In my experience the wrong oil grade will knock off 10-15 MPG in the most extreme cases. Overfilling after an oil change also leads to another drop in MPG. Lower tire pressures will not help if the tires have been changed to anything but OEM rubber. I would recommend that you inflate your tires to a good pressure level if they have been changed to something softer.

An issue with the emissions control or fuel system will likely cause one or more DTC's sooner or later and that is something that may help to get fixed. Since you have not mentioned seeing any CEL light I will assume that the likelihood things may have reached that level a little remote.

Anyway, what kind of servicing was performed around the 50K mark?

Cheers;

MSantos

nursemike

2 years ago

I had the same issue with my 2006 HCH. Try testing the 12 volt battery under the hood. The IMA battery charges the 12 volt battery via a DC-DC converter (step down) and a dying 12 volt placed a burden on the large IMA battery. The 12 volt batteries tend to not last more than 3-4 yrs tops. Try load testing th battery.
I love my HCH too, so much so that I got an Insight for my wife with the same powertrain. Good luck resolving the issue.

nursemike

2 years ago

Did you get a CEL for the O2 sensor, or was it a hunch based on the behavior of the vehicle? I'm curious if an O2 sensor could be dying and affecting performance without triggering a CEL.

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Mendel Leisk
Senior Member

2 years ago

If the O2 sensor question is directed at me: it was just a hunch, from what I'd read. This was on a 91 Accord. There were no Check Engine Light warnings.

P. Tompkins

2 years ago

I'm told by my dealership not to use a fuel with ethanol in it. As few as 4 consecutive tanks with ethanol in it will put it in the shop.
13

Gary

2 years ago

Ethanol? How can one determine which brands in which parts of the country are adding ethanol. Ohio, where I live, had a law requiring pumps to be labeled, but the law was repealed around 2005. I would avoid ethanol if possible, but can anyone tell me how.

Buck

2 years ago

Had the same sort of thing happen to me with my 2007 Civic but it was a result of changing my tires.

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