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Old 07-10-2011, 11:11 AM   #1 (permalink)
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1997 Honda Civic DX gets horible gas mileage?

Hello all,

I've just recently transitioned from a 2001 Auto Kia Rio to a 1997 Honda Civic DX (also auto) under the unambiguous conviction that it got better gas mileage: virtually every website I've visited stated that it always got between 30 and 39 mpg. However, this does not seem to be the case for me. In fact, the Civic has a much bigger tank and seems to deplete to empty given the same miles. I have calculated my MPG various times, and have received an average of app. 21mpg. Is there any reason why this should be so? I know the car has cool-air intake, but I drive at max 55 mph on highways, and it doesn't seem to be the prodigious economy car it has been made out to be. At best, it seems to be on equal standings with the Kia.

Also, incidentally, I've noticed that cops pull me over a LOT more in my Civic. I actually drive much more economically-- and therefore (at least seemingly) safely-- but they seem to be glued to the conviction that if a car looks old and... civic-ish... there must be something wrong with the driver. I've never gotten pulled over *once* in my Kia within a year; within a month I've gotten pulled over 5 times with the Civic.
Has this ever happened to anybody else? I'm starting to think that keeping my Kia would have been much more 'economical', just because it appeals to the fatuous minds of cops.

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Old 07-10-2011, 12:39 PM   #2 (permalink)
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It is the auto, so it will be lower than my manual. But that's too low for a DX, it seems to me. Has it been checked out by a mechanic? Do you have the skills? Compression? Sparks? Brake drag? and etc... In normal driving in the city you should get probably 25mpg on an auto. But that is just the EPA (my guess of it too).

See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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Old 07-12-2011, 02:49 AM   #3 (permalink)
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If it has a cool air intake, is there evidence that anything else has been messed with under the hood? Any aftermarket bits that may have been incorrectly installed etc. Stock size wheels and tires? Stock exhaust?
"Don't look for one place to lose 100 pounds, look for 1600 places to lose an ounce." - Tony DeFeo
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Old 07-12-2011, 10:14 AM   #4 (permalink)
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EPA rating for the civic dx with the automatic is 24/32mpg, Honda's don't tend to like after market air intakes so that is going to drop it down right there, same with an over sized exhaust, so look under it to see what else has been screwed with.
It would be well worth you getting a scan gauge, not only for improving your driving style but for checking things like engine coolant temp, if it's going into closed loop and that everything else is running right.
Flushing your transmission and doing a full tune up could be worth while as well.
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Old 07-12-2011, 12:57 PM   #5 (permalink)
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Check the battery. Those tiny things wear out faster than some cars with bigger batteries.

Any Check Engine lights? A faulty O2 sensor could give you bad mileage and it's not uncommon for cars of this age. Some auto parts stores will scan your error codes for free.

11-mile commute: 100 mpg - - - Tank: 90.2 mpg / 1191 miles
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Old 08-10-2011, 04:30 AM   #6 (permalink)
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I have definitely noticed increased attention from the #&^%*&# #&(^$#&*^$ @!)(*$^%* @*)%(@(hole cops in my Civic. Even when it was quiet I got more attention. #@)!@ #&@)@ !)$&* cops. But, 5 times in one month, what are you doing while driving?

My parents' 2000-ish Civic autotragic would always get mid 30's on the highway and mid 20's in town. Time for some maintenance and get rid of that cheap "cold" air intake?
1992 Civic VX

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Old 08-10-2011, 02:20 PM   #7 (permalink)
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I would have a tune up done by a competent mechanic. Thats the best place to start. You should be getting mid 30's at least on the highway. I have noticed that when I'm driving under the posted speed limit, the cops have a tendency to check me out more than when I drive over it. Just suspicious I guess.
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Old 08-25-2011, 07:19 PM   #8 (permalink)
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Not knowing the background or mileage of the car, you may need to perform a good bit of maintenance that has been "deferred" by the prior owner. Number one on the hit parade is a timing belt. Do you have any maintenance records showing when it was last replaced, if at all? Honda engines are interference fit engines. If the belt breaks, the odds are all too high that the pistons and valves may have a rude introduction to each other. Transmission fluid change, and perhaps brake fluid. Check all four wheels when jacked up to make sure that the brakes are not dragging. A dirty air filter can cause a surprising loss of mileage.

Do the recommended tune-up (look out for oil inside the distributor cap) and clean the induction system as well and run some seafoam or BG 44K through the gas tank for starters.

How is the alignment? If the tires show any odd signs of wear that could be a problem both in terms of tire wear and mileage.

Then keep records of your miles driven, the conditions and amount of fuel.
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Old 08-27-2011, 05:03 PM   #9 (permalink)
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Possibly a bad 02 sensor. I've had them go bad and seen the mileage on my '88 Escort drop by as much as 25-30%.

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Old 11-19-2012, 07:40 PM   #10 (permalink)
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Just a couple of things in addition to the good advice you have received so far.

Is there black smoke coming out of the exhaust and does it smell "rich" (gasoline odor)? If might very well be an O2 sensor, but could also be a temperature sensor. Either one of these should show up as a check engine code. There is also the possibility that the throttle body needs a good cleaning. (How does the engine idle?) There is also an EGR assembly that could get "gunked up" and could affect mileage.

I would also suggest checking for a dragging brake. Just jack the car up and spin the wheel by hand. It is also possible that one dragging brake could make the car pull to one side or the other either just going down the road or when braking.

I strongly second the advice about checking into the maintenance history of the timing belt. If you can do this yourself, you can save a lot of money. Make sure to check if the water pump is supposed to be changed at the same time as the timing belt on your car...I don't recall about your particular model, but many of the Hondas do.

Oh, about the Seafoam or BG 44K. Run it through the gas tank a couple of times just to make sure you have the fuel system good and clean. Thereafter you can do it periodically as preventative maintenance.

And when you are doing the tuneup, make sure to replace the fuel filter as well as the air filter. Make sure to use the weight of oil specified for your car. Sometimes people put in oil that is too "heavy" for the car and it does not do any good.

I live in a hot part of the country and like synthetic oil. I notice you are in an area where it gets cold...the synthetic oils are good there too. Make sure to use only Honda approved automatic transmission fluid. Their transmissions are very particular about being fed "the right stuff".

Good luck!

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