I bought a 1997 Honda Civic HX

[RobertSmalls]

Originally Posted by Titanium

I have a new genuine Honda thermostat with gasket, but I have to have a specialized extension to get that off.

If it's anything like the Insight, then they assume you have a 1/4" drive 10mm socket and extensions for a number of things on the engine. The torque specs on the Honda are low, so 1/4" drive works out great.

[Titanium]

Originally Posted by RobertSmalls

If it's anything like the Insight, then they assume you have a 1/4" drive 10mm socket and extensions for a number of things on the engine. The torque specs on the Honda are low, so 1/4" drive works out great.

Robert

Everything has been easy to get to and work on this 1997 Honda Civic except the thermostat. If I had the right extension the thermostat would be easy to replace. I will buy the extension I need.

A friend of mine who owns an older Honda Civic said it is a good idea to replace the coolant heat sensor because they can go bad and not read the correct temperature.

Within the next year I will probably replace every engine belt in the car, put a new water pump on and replace every radiator hose also. I'm planning on driving this car a very long time and the goal is to never break down. Plus I probably will drive this car on some long distance trips next summer.

[lnknprkfn]

although this is very late, you will find that you dont need a crazy extension if you took the airbox and intake hose off when i got my 97 Civic HX from a friend for 500 i got the head gasket replaced then it was discovered their was a leak in the water pipe that ran across the back of the block from the thermostat housing to the water pump and with the airbox off it was alot easier to work with..

and my civic i put Pulstar Iridum pulse plugs and filled it with 3.5qts of mobil 1 synthetic extended performance and a K&N performance filter(Would of stuck with matching Mobil1 Filter but it was rusted from moisture caused by water leaking into trunk from welds near the trunk gasket.) so other than all that and needing a new o2 sensor and possibly cleaning of the egr passageways i would probably nearly restore my 111k mile civic

[Titanium]

I have owned my 1997 Civic HX for over a year now. I get 39 MPG overall in this car and it is still 100% all original and stock. I drive to work 70-75 mph also. I use the stock NGK V-Power spark plug that is recommended in the Honda owners manual in this car. I talked to a guy who worked at Auto Zone who also owned a Civic HX. He said that him and another friend of his who also owned a HX tried many different spark plugs and the stock NGK plug got the best milage. The worst spark plug they tried dropped the milage down 5 mpg.

I also use Pennzoil Ultra Synthetic 5w-30 oil changed every 4K in this car. I keep the Mobile 1 extended performance oil filter on the engine for 8 K(two oil changes). I had the timing belt and water pump replaced recently at the Honda dealership. I have 192 K on the car now.

I need to buy one of those ScanGaugeE Fuel economy gauges for this car and try to get the best MPG out of it.

[brucepick]

Glad things are going well with your HX.

Be advised - a ScanGauge will not give accurate mpg info on an HX. An MPGuino costs less but can be very accurate. The ScanGauge however will give you lots of useful data such as engine coolant temp, throttle position, system voltage, and more.

The reason the SG won't read out mpg accurately is that it can't measure fuel use. It gets mass air flow sensor data from the computer. Then it assumes standard stoich air:fuel ratio and so derives fuel quantity. It gets distance data from the computer and so has enough data to derive mpg.

However the HX has lean burn (LB). When in lean burn it's not running at stoich, but far leaner. So the SG assumes you're burning much more fuel than you really are. True that there's an adjustment factor you can dial into the SG. However the percentage of time that you're in LB is not consistent. You need something that actually measures fuel usage.

The MPGuino does that. You wire it to a fuel injector and to the VSS. Two other leads go to power and ground sources. Yes, it's a real do-it-yourself job but it can be accurate within 0.1 gallon or less when you fill up. Have a look here:
OpenGauge / MPGuino FE computer - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

[Titanium]

Originally Posted by brucepick

Glad things are going well with your HX.

Be advised - a ScanGauge will not give accurate mpg info on an HX. An MPGuino costs less but can be very accurate. The ScanGauge however will give you lots of useful data such as engine coolant temp, throttle position, system voltage, and more.

The reason the SG won't read out mpg accurately is that it can't measure fuel use. It gets mass air flow sensor data from the computer. Then it assumes standard stoich air:fuel ratio and so derives fuel quantity. It gets distance data from the computer and so has enough data to derive mpg.

However the HX has lean burn (LB). When in lean burn it's not running at stoich, but far leaner. So the SG assumes you're burning much more fuel than you really are. True that there's an adjustment factor you can dial into the SG. However the percentage of time that you're in LB is not consistent. You need something that actually measures fuel usage.

The MPGuino does that. You wire it to a fuel injector and to the VSS. Two other leads go to power and ground sources. Yes, it's a real do-it-yourself job but it can be accurate within 0.1 gallon or less when you fill up. Have a look here:
OpenGauge / MPGuino FE computer - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

Wow, great info. Thanks Brucepick. What mods do you recommend that I consider doing to my HX to increase the gas milage? My car is 100% stock.

[Titanium]

Brucepick

While I'm waiting to buy one. I'm curious as to what freeway speeds and rpm's produce the best mpg in a Civic HX?

I drive 71 miles round trip on my daily commute and most of that is on the freeway. I usually drive 70-75 mph on the freeway. I have been averaging 39 mpg. The rpm's are quite a bit higher at 75 mph vs 70 mph in my HX.

[Titanium]

Originally Posted by brucepick

Welcome to the club! I've had mine just over two years now.

Plugs: NGK as spec'd by Honda. ZFR4F-11. This NOT the same as other Civics of the same year. I found them at Honda dealer (sometimes) and at Pep Boys, where I do not usually get parts.

OIL: Mine burns oil. About 20 oz per 1000 miles. Not all burn oil but it's not uncommon.

Oh yeah - it holds only THREE QUARTS! I've seen other HXs, pulled the stick and oil is far over the mark. Nobody believes it only holds 3 qt. You can bet the previous owner/maintainer overfilled it most of the time. Put in 3 qt when you change it. After a quick level check, spin it over, drive to warm it up and then drain down for 1-2 hours. Then check it and see if you agree.

I found that WalMart Synthetic 5W-30 blew right through the engine. Didn't burn much for a couple hundred miles after a change, then whooosh! Far more than 20 oz/K miles. My theory is that the "viscosity enhancers" which create the high viscosity number broke down quickly and then it was thin oil, maybe actually 5W-20. Tried a lot of things including mixing in 8-16 oz of Castrol 20W-50.

I settled on Rotella T6 synthetic, which is 5W-40. It seems to hold it's 40 rating (viscosity in hot engine state) so it doesn't blow through. Now it's using about 20 oz per 1000 miles. It's a diesel oil but also exceeds the spec's for the HX requirement. I get it at WalMart, and right now it's on sale at Advance Auto.

I talked with a good indy Honda shop, they wouldn't be afraid to run it on straight 20-50 if that's what it took to keep it from burning. In other words: yes, the car is spec'd for 5W-30 and 5-40 is thicker, but being thicker would not be an issue if the thin stuff blows right through. I like having the 5 rating for cold state, especially with winter coming. I don't want really thick oil in there at startup.

My experience with the Pennzoil Ultra Full Synthetic 5w-30 that I have been using in my 1997 Civic HX and my 2003 Chevy Cavalier is the synthetic oil is slipperier than the conventional motor oil I had been using. Both of these cars do not burn or leak any oil. The full synthetic blows past the piston rings easier than the conventional oil. I know this by experience due to I have to check the oil level more frequently in both cars to make sure it is on the full mark. I just keep it topped off on the full mark.

The 2003 Cavalier would be down about 1/2 a quart with conventional oil at 3,000 miles with no top offs. This car holds 5 quarts. With synthetic in this car I am probably adding almost a quart of oil during my 4,000 mile oil change intervals. I know this car very well since I have owned it since it had 35,000 miles on it. The Honda Civic HX I instantly switched to synthetic when I bought it and also switched over the Cavalier to synthetic at the same time. I had always used conventional oil in the Cavalier and it had always only been down no more than 1/2 a quart using conventional oil at 3,000 mile oil change intervals. The synthetic oil is blowing past the rings a little more is all and both cars are doing the same exact thing with this oil. One benefit is I am adding new oil when topping it off. I check my cars oil around every 1,000 miles with synthetic.

Conventional oil is thicker and does not blow past the piston rings as easy in my experience.

When they say full synthetic oil is slipperier than conventional oil and that synthetic oil lubricates your engine better I do believe that.

I would not recommend synthetic oil for a car that had a bad case of burning oil though. It would want to blow past the rings more than conventional oil and probably make things worse while also being more expensive. I would use conventional oil for a problem car.

[some_other_dave]

Originally Posted by Titanium

I'm curious as to what freeway speeds and rpm's produce the best mpg in a Civic HX?

Like most cars, the best MPG is achieved when running as slow as you can stand in the tallest gear the car has. Try 1800 RPM in 5th gear. If the engine doesn't shudder from that, and you can cope with the relatively slow speed, that ought to give you good steady-state MPGs.

-soD

[brucepick]

Hey there, Titanium,

I'll second what Some Other Dave wrote - top gear at the lowest speed possible should give the best FE. However you might not want to do your commute at about 45 mph, which is approx the functional bottom speed for 5th in my HX. 40 mph works, but I'm not sure I'd want to do that long term. So, see below for some thoughts re. achieving Lean Burn in the HX. In my car, lean burn is usually available between about 61 to high 70's mph in top gear. Excellent for highway running.

For the HX I really recommend a ScanGauge 2 (or later??) with one of the X-Gauge optional gauges set for a Lean Burn indicator (LB). I might have posted the how-to for that earlier in this thread, but I can send it by private message if you ask. Net mpg increase from LB versus regular air:fuel ratio is somewhere between 10-15% so there's a real gain in knowing when you've gotten it into LB, from the gauge readout.

My car is kinda finicky about going into LB. I've written and talked with others who have HXs, and one guy with a Gen. 1 Insight which also has Lean Burn, and their cars aren't as finicky as mine. My point is, I can't say "put it at x rpm and don't stomp on it, and you'll be in Lean Burn". In my experience, it's not that simple - I wish it were.

You also want an MPGuino to read actual fuel consumption. About $50, but it's truly a do-it-yourself project. Well worth the effort though.

Mods? You get to choose, truly. Have a look at my car's page here:
Details: Lean Burn Civic - 1997 Honda Civic HX Fuel Economy - EcoModder.com
You can see the sequence I did the mods - easier stuff first. I keep putting off some rear wheel skirts. I plan to go down only about half way so I won't need to bow them out. I mentioned it because it should be relatively quick + easy.

And have a look at California98Civic's DX. Not a lean burn car but he's doing very well with it:
Details: Black and Green - 1998 Honda Civic DX Coupe Fuel Economy - EcoModder.com