mililani

Hi folks,

I've posted about this before and barely got any responses. Thought I would try again because I now know unequivocally that something is wrong with my car.

First, I was wondering, would anyone do me a favor and help me out? Can you check to see how much RPM's your 7th gen Civic runs at near 65 mph? Before, I remember my 2001 civic LX would run around 2000 RPM's at 65 mph. Nowadays, it has to get above 2500 RPM's to do that. I used to get 44 mpg all the time driving highway miles (by the way, my method for determining mileage: I fill up the gas, check the gallons pumped, and divide that into the trip odometer). That was about 1-2 years ago. Nowadays, I usually get 33-35 mpg. And, I know it's not the fuel type, which I erroneously see trumpeted around here as being a fuel economy killer. My wife has an 2009 civic LX, and we go to the same gas stations. We just got back from L.A., driving around 70 mph, and she averaged near 43 mpg the whole trip. So, I know it's not that. I also make sure the tires have correct pressure. I change the oil and filters regularly. I also did the transmission fluid using Honda ATF. The car also had timing belt redone a few years ago. So, I'm wondering if this is something else.

I found another thread about poor gas economy problems on this site, and someone mentioned a friend had a similar problem, went to Honda to get diagnostics, and they found a problem with his tranny. OK, that makes sense to me given all we know about the crappy AT on these 7th gen civics. My car is running at much higher RPM's than it used to, so that does sort of make sense. Anyways, I'm just wondering if anyone has any suggestions or bright ideas before I go to get some diagnostics run.

Thanks for listening.

GolNat

iTrader: (7)

Check here for RPM's:

https://www.civicforums.com/forums/1...60-65-mph.html

Have you had a tune up? Changed the air filter? Do you have the same tires you had when you were getting 44MPG?

Could be the tranny slipping or torque converter. How many miles are on it?

mililani

Hi GolNat,

Yeah, I posted that before. I was hoping for an update before I take it to the shop.

Those are all good questions. I should elaborate more.

Yes, tires are still the same as before. They are about 5 years old, and my mileage problem has been going on since a year ago. Before that, I would always consistently get 44 mpg from HWY driving. I know this for a fact because I used to drive 400 miles once every 2 weeks on open HWYs with no traffic and going about 60-65 mph.

I haven't changed the air filter lately, but I just checked it and it looks pretty clean to me. I guess I could just change it and see.

It has about 140k miles on it. And, yes, the tranny has been slipping for awhile. It will sometimes slip out of first gear, but if I back off the gas, the tranny will engage second gear no problem. It only happens every so often, and it's typically from cold starts. Although, this was also happening when I WAS getting really good mileage. So, I'm not so sure about that.

I've read several times that the O2 sensor often go bad on our Civics. Would that cause a large drop in mileage?

ezone

Certainly. The O2 sensors can have major influence over fuel control.

mililani

Much thanks for the replies, everyone. I'm going to look at a couple of things over the next few weeks and see what helps: air filter, O2 sensor, clutch, etc...

sdaidoji

iTrader: (1)

but most of all, if your car is running higher RPM now at same speed, suspect is trans not shifting to higher gear. have you confirmed that?

mililani

I'm not sure. But, I guess, according to the RPM poll on another thread, I'm within ball park average.

Although, my wife's 2009 civic LX runs much lower RPM's. Her car runs 65 mph at 2000 RPM's. I'm like, near 2500 RPM's to maintain 63 mph.

ezone

Apples and oranges.
Completely different drivetrains.
You cannot compare these.