98hx only getting 25-28 mpg?!?!?!

[darcane]

Originally Posted by Old Mechanic

You need to replace the thermostat, preferrably with an OEM Honda unit. Make sure the system is properly bled when you refill the coolant. IF you dont when really cold weather arrives, you probably will not have any heat to warm the car. Gauge should read around half way within 1.5 miles.

Maybe, maybe not.

I don't know if it's true on all Civics, but on my '01 the factory gauge is all but useless. It has no numbers, just evenly spaced tick marks with one red one at the top. Based on what my Ultragauge reports, normal operating temperature (180°F) is only about 1/3rd of the way up the gauge, when the fan turns on (206°F) it's still less than halfway. When my headgasket blew and it was overheating (~230°F) it finally got to halfway. I have no idea how hot it would have to get to hit that red mark, but I bet the head would be warped.

So, good advice on the thermostat, just be aware that the gauge may give you poor information.

[darcane]

Also, more details about the car:
Is it an auto or manual?

Is it stock or does it have modifications? In particular:

• Large wheels
• Cold air intake
• Header
• Big wing/spoiler

All of these can negatively impact economy.

[California98Civic]

Originally Posted by 98civHX

Yeah, I'm new to this site. I clicked on your profile and tried to PM you but I wasn't sure how to do it. But, I just sent you a reply in my email as well and I'll edit my rmail out of the previous post.

I just sent the google-drive file/link to you... you should be able to download it. Did you receive it?

[user removed]

Originally Posted by darcane

Maybe, maybe not.

I don't know if it's true on all Civics, but on my '01 the factory gauge is all but useless. It has no numbers, just evenly spaced tick marks with one red one at the top. Based on what my Ultragauge reports, normal operating temperature (180°F) is only about 1/3rd of the way up the gauge, when the fan turns on (206°F) it's still less than halfway. When my headgasket blew and it was overheating (~230°F) it finally got to halfway. I have no idea how hot it would have to get to hit that red mark, but I bet the head would be warped.

So, good advice on the thermostat, just be aware that the gauge may give you poor information.

Benz tech bulletins stated their cars could run as high as 256 degrees without issues as long as coolant was 50-50 mix and proper pressure cap (13 psi). Probably lost the head gasket then ran hot.

regards
mech

[user removed]

The old wire wound bimetallic gauges used in the first z cars were the same as those in a F15 fighter jet.

Good advice anyway, the real question is how long does it take to get to operating temp.

180 degrees at the top hose, you can tolerate for a few seconds placing your open hand on the surface of the top hose.

regards
mech

[98civHX]

Originally Posted by darcane

Also, more details about the car:
Is it an auto or manual?

Is it stock or does it have modifications? In particular:

• Large wheels
• Cold air intake
• Header
• Big wing/spoiler

All of these can negatively impact economy.

It's all stock and manual transmission.

[98civHX]

Originally Posted by California98Civic

I just sent the google-drive file/link to you... you should be able to download it. Did you receive it?

Thanks James, I'll look at it after work.

[97-civic-ex]

On thing that really affects mpgs on Honda lean burn is EGR system condition. Are you getting any check engine lights? Make sure the check engine might comes on for a few seconds at start up to verify the bulb is functional. The main issue with the EGR system is clogged passages and sticky/faulty EGR valve.

[98civHX]

Originally Posted by 97-civic-ex

On thing that really affects mpgs on Honda lean burn is EGR system condition. Are you getting any check engine lights? Make sure the check engine might comes on for a few seconds at start up to verify the bulb is functional. The main issue with the EGR system is clogged passages and sticky/faulty EGR valve.

No check engine light at all. I figured that I would clean it out since I've read that it helps out with mpg. I just sea foamed the car and I've notice little improvements, especially with the idle. If someone thinks I shouldn't clean the egr passage ways please let me know.

[vskid3]

Are you sure it's stock? Post the RPM in fifth gear at a certain speed and we can check that the transmission didn't get swapped with a lower geared one at some point.

Only reason not to clean the EGR is if you don't think you'll be able to put it back together correctly.

Your short trips certainly aren't helping, but you should be able to get at least in the 30s in all but the worst conditions.