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I have a question about the transmission in my 2008 Civic LX 5AT. How do I know for sure when the torque converter is locked up in top gear ? Does it also lock in 4th ?
What speed ? I am able to get into fifth gear at 37 MPH and go as low as 33 MPH( on flat ground,with a careful foot)without a downshift. My usual commute has about 7 miles of 35-40 speed limits and I am willing to bend the law a bit to optimise my efficiency. This is my first automatic trans car , so I'm kinda new to this.
Can anyone here advise ?

While I can't provide exact answers to your questions there is a trick that other Honda owners with automatics use with success. On flat roads you can coax the transmission to shift up from 4th to 5th at speeds around 35 mph by shifting briefly into neutral then back to drive. You will see the revs drop to confirm the shift.

In my own car (Accord) the upshift to 5th would not otherwise occur until about 40 mph. I have a local road where I can use this method to drive several miles at 35 mph while staying in 5th.

Another method is to ease off on the gas when on flat roads which not only may encourage an early upshift but also changes the ignition control to a leaner setting. Those with Scangauges can monitor this closely.

Lots to learn if you're interested. Others here know way more about these methods so "stay tuned".

Cheers,

Roger

when it is locked up, engine speed and rpm maintain constant ratio.

generally ats only lock up in top gear. If you accelerate hard enough, you will "lock" the ratios.

The 5 spd AT is quick to upshift so you have to be very light on the throttle to keep it from downshifting to accelerate. 37mph is where it will always shift into 5th. rpms are at about 1650 at 50mph (compared to 2200 for my eclipse).

If you accelerate more than lightly, or load the engine at any amount, it will downshift.

I've gotten, let's see, 437 miles from 10.6 gallons of gas on a long highway trip (600 mi rt total) at between 50 and 80mph. a/c cycling. Around town, you can look for numbers just above epa driven regularly.

Roger and Ricardo , thank you for your help. If I had a ScanGauge , would it show me when the torque converter locks ? I THINK it is locked , but when I barely tickle the accelerator,the revs jump by about 150-200. Does that mean it unlocks that easily ?

Half of my 15-mile commute is through dense suburbia, the other half starts to get sort of rural(higher speeds,never over 50 mph,fewer stops). I'm averaging about 42 MPG for the last three tanks ; it goes down as low as 32 MPG in the worst part of winter. I have records of all my fills for the last year and a half,one of these days I will get it on a log here.

In steady state driving when the converter is locked, moving the accelerator won't cause a change in rpm relative to speed. If you release the pedal, then tap lightly, you will see a slight uptick, which indicates unlocking, however it re-locks after a couple seconds of steady throttle in fifth and dips back down to normal rpms

Roger and Ricardo , thank you for your help. If I had a ScanGauge , would it show me when the torque converter locks ? I THINK it is locked , but when I barely tickle the accelerator,the revs jump by about 150-200. Does that mean it unlocks that easily ?

The ScanGauge can't show you directly when the torque converter is locked, but it would show small changes of RPM.

When in torque converter lock I find that "barely tickling" the gas doesn't change the RPM. I had the opposite situation to you: I was seeing the effect but I didn't know about torque converter lock. I had a section on my commute where the road inclined and I wanted just to hold speed. So I'd slightly increase pressure on the gas pedal and the damn rpm didn't change, until a point where the rpm would suddenly jump to about 2,500 rpm. Obviously I was seeing it drop out of lock and down-shift.

In lock, I think it's about 1500 rpm at 45 mph, rising to 2100 rpm at 65mph. But the Civic's not my commuter so I'm going from vague memory.

Half of my 15-mile commute is through dense suburbia, the other half starts to get sort of rural(higher speeds,never over 50 mph,fewer stops).I'm averaging about 42 MPG for the last three tanks ; it goes down as low as 32 MPG in the worst part of winter.

I managed 44mpg on 2 spring tanks, but my commute is about 20 miles, more 45 to 55 mph over rolling hills and the city traffic on either end is light, with few stops. So that 42 mpg sounds reasonable.

My 44mpg was achieved with tires at 41/39 (I think), DWL, NICE-ON and smart-braking/light timing/threading the needle.

I have records of all my fills for the last year and a half,one of these days I will get it on a log here.

I you ask very nicely you might be able to provide of the admins with a file in a particular format that he can load into the system. Otherwise, I suggest you log backwards: every time you fill up your car, add your new fill and the latest old fill that you haven't logged. You'll get your latest and most relevant history in first and if you stick at it, eventually you'll catch up.

INATM , I was hoping you would chime in. Your comments and insights are usually right on the money. Thank you so much !