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Hi all I'm new to this forum, Just recently bought a 98 civic dx 5 speed to use as my daily driver. I've hear lots of good things when it comes to MPG for these cars but I don't see it I havent driven the car much yet because I still need to get tags for it so I just been doing most of the driving around my neighborhood just for fun since it's my first stick shift car. when driving the needle doesnt' move very much if not at all but when I park it over night and get in the next day the fuel needle looks like It plummited a few cm. No fuel leaks that I can see or smell. Where should I start? Has about 144k runs smooth last owner was a mechanic and told me all the repairs he had done: New cat converter, spark plugs (cant remember if he chainged the wires), fuel filter, and distributor. Needs new battery.

 
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i'd say it's too early to tell. you'd need to get some good drive cycles and proper warm up, then log your miles per full tank and that should give you a better idea of your consumption.

 
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driving around the side streets will prolly give the worst mpg anyway. these cars do best on the highway 55-60mph.

 
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I don't know about everybody else civics but my fuel gauge is wildly inaccurate so I wouldn't go by where it reads. Put a few tanks through it and do the math and see where it ends up.

For example, if I go around a hard corner it can go from 1/3 tank to the fuel light going on. I park in a place that isn't totally level and it's out by about 1/4 tank. From a full tank the needle doesn't budge until I hit 200 km then it drops down 1/3 tank. Use your tripometer for more accurate measurement.

btw - I do entirely hwy driving and it's always between 38-42 mpg

 
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thanks guys for chiming in. I'll start doing the math at my next fill up. since this is my first 5 speed I want to get the best fuel economy out of my civic. Just curious as to when I should shift for optimum mpg? Lately I've been shifting around the 2000-2500 range depending on wich gear im in. I don't let the engine not get to loud cuz i'ts just working harder. Should I keep this up? By the way anyone seafoamed there civic? My throttle body is gunked up from the plate down.

 
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My DX didn't come with a tach but when I installed it I did the up shifts according to the speeds my owners manual recommended. It ended up being around 3000rpm. My fuel efficiency drops if I drive above 60 mph which not so coincidently is above 3000 rpm. I seafoamed it 1 year ago (just in the gas tank) and it didn't really make any difference but my engine is pretty much in new condition anyway.

 
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Ok so now i'm having another issue, I got a check engine light with the P0420 that I hear is common with the honda and another pending code.After the light came up I've been having an issue with the car trying to stall when I crank it up doesn't matter if it's cold or warmed up. would a bad cat be causing the failed stalling issue or could it have some thing to do with the o2 sensors Or maybe even the charging system? I have the elm327 usb scanner so any advice as to how I can use it to find my problem would be great.

 
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P0420 code is defined as "Catalyst system efficiency below threshold" a.k.a a defective or non-existing catalyst. so yes it's a bad cat I'm afraid.

 
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Will it be ok to drive it for a lil bit until I get it replaced? How much am I looking at for an oem replacment. Are there any aftermarket ones that work just as well in place of an original? I hear that aftermarket cats don't last as long but there has got to be a less expensive alternative than the original.

 
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I finally sucked it up and decided to take it in to a shop, the tech came out and told me that from the diagnostics the upstream O2 sensors wasn't working right and that I have a hole in the exhaust system some where after the cat. I bought a bosch o2 sensor from autozone, put it in and my car was idleing very low to the point where it sounds like it's going to stall, around 150 rpm. I still had the old down stream sensor in I don't know if maybe the two defferent brand sensors don't work well to gether or some thing. For now I just put the old one back in. Any advice would be great, I've been throwing time and money around trying to get this damn issue figured out.

 
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I'm in your boat too. I picked up my 2000 ex and have been having headaches left and right. Tie rods both bad. Replaced. Won't rev pass 3000 rpm. Replaced upstream o2 sensor. Code 14 came up. Cat bad. Replaced. Old one was high flow cat. Idle surges. Cleaned iacv. Relearned idle. Still idles up and down but way better. Gas mileage saving is not worth it. I'm going to sell next spring to go back to Subaru. I'm a Honda tech, but tired of Honda idle issues. Friends have it, neighbors have it. Sometimes car parking next to me at red light has it. My old 92 prelude has it. It had a 25k mile h22a4 swap. Never got it fixed, after 2 years, sold it. So tired of it all to save $300 a year and giving up power.

Add. Vtec selanoid leaking...I think. Replaced gasket and triangle gasket on top too. Still leaks. Replaced head gasket, waterpump and timing belt. Still leaking and reving.

 
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Yeah reliable cars my ***, seems like folks WAY over exaggerate when when talking about reliability, bull ****. All i'm thinking is, when ever I get this damn issue fixed what else is gonna pop up? the repais aint gonna cover themselves in fuel savings. I'm just about close to selling this junk and get back what I paid for it

 
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My 1999 Honda Civic Si with 150,000 miles on it and the 1994 Honda Del Sol I sold this fall with 325,000 miles, were both idle problem free. I believe if you compare a 200,000 mile Subaru with a 200,000 mile Civic, the Civic will usually have had the least money spent to keep it running.

 
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I recently purchased a 97 Civic also really excited about saving on gas. At first I did find it amazing that $20 would give me 3/4 of a tank, but my keeping track of my miles Ive only driven 74 miles and my gas gauge is already marking a bit less then half a tank.... WTF!!!??

 
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usually on older cars you need to at least do a minor tuneup (plugs, wires, dist cap and rotor, clean intake system parts, etc).

 
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Whats the process for clean intake system parts? Is that something one can do at home or is taking it to a shop a better option?

 
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pretty easy to do at home. remove the intake and filter, then start removing all the easily accessible parts around or on the intake manifold like throttle body, iac valve, fast idle valve, etc. and spray them with carb cleaner inside. the only tricky one is the iav with coolant lines going to it. just make sure car is cold and you remove the radiator cap to depressurize the system first.

 
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Hondas are pretty notorious for their fuel gauges being off. In any case a new air filter wouldnt hurt.

 
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I know this post is kinda old, but my car has the same, well had the same code for the cat being bad. You can get around it by not having the monitor run so it won't pop up anymore. If you're interested, I can send you the steps so you don't have to deal with it until you save up enough to eventually get it replaced. OEM replacement is around 500-600 IIRC depending on where you look.

 
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yeah this is old lol apreciate your input though, unfortunantly I was in a car accident so my civic is done for. I'm looking at buying a 2000 honda civic lx with 157K. I'ts an auto, I went to check it out and the check engine light is on for the p0420 and when test driving the tach would wobble up and down and the transmission doesn't want to shift to third gear until 3500 rpm or so. any advice would be appreciated, this guy is suppose to come deliver me the car after he gets the title. so far his been pretty honest about the car.