Civic fuel consumption, again

A) yeah, city traffic can be brutal to mileage, especially if you punch it when the light turns green.

B) do you have enough miles on it to start being concerned with mileage? Typically it's not fully broken in till around 10K.

EPA mileage estimates are determined through dynamometer testing in a laboratory, and among the factors reducing actual gas mileage that are not considered in these tests are rolling resistance of unpowered wheels/tires, aerodynamic drag, non-productive operation (engine running with no forward progress, as occurs at traffic controls or in stop-and-go traffic), ambient temperature (affecting intake air density), and altitude (also affecting intake air density). City and Highway mileage ratings determined in the laboratory are adjusted downward by 10 and 22 percent, respectively, in an attempt to compensate for these and other factors, but Consumer Reports have consistently determined, using their own mileage testing protocol, that the EPA mileage estimates posted by automakers for new vehicles are optimistic, sometimes by as much as 30-40 percent.

And yet, my '93 Accord consistently got 10-20% above EPA estimates on the highway. Go figure.

This may seem like an asinine question, but what is your process for calculating actual fuel mileage? Also, what is the elevation and range of mean daytime temperatures where you live? I ask the latter because lower elevations and lower mean ambient temperatures, in comparison to the location of the automaker's test facility, will result in comparative mileage improvements, ceteris paribus, due to more dense fuel/air mixtures prior to combustion.

I calculate my mileage the old-fashioned way. Start with a full tank (not overfilled), drive the trip, fill up again, take note of how much gas I put in at the end of the trip and how far I travelled, and do the calculations.

I live in southern Ontario (Canada), where spring and fall temperatures range anywhere from 5-15 Celsius (41-59 Fahrenheit) and summer temperatures range from 20-30 Celsius (68-86 Fahrenheit). The elevation is somewhat flat with moderate hills in places.

EPA rated the '93 Accord automatic at 28mpg on the highway. My car consistently averaged 32-34mpg on the highway under normal conditions. In fact, it even got 36mpg on one occasion a few years ago. And BTW, those are U.S. gallons in my mileage figures, not Imperial gallons.

I have an Si, and it is pretty close. I get an average of about 27, overall driving. The EPA rating is 23/31, so this is about right. When I drive mostly highway, I sometimes do better than 31...

I drive in also in a similar condition (Southern Ontario, Canada) and got the average 1 year mileage (Winter+ Summer) as 35mpg (fuel logbook available at ontariogasprices.com). During Summer mileage was average

40mpg with maximum of 50mpg. I was suspicious, obviously. But that was a trip from Waterloo to Toronto and back to Waterloo.

What is overfilling, by the way. I fill the tank until the nozle stops automatically.

with a full tank (not

with a full tank (not

That is proper filling; overfilling happens when more gas is squeezed in by waiting a minute and trying to get some more to trickle in or (even worse) by pulling the nozzle partway out of the neck and "topping up" the tank that way. It can get liquid gasoline in the charcoal canister through the vapor line to the tank, which saturates the charcoal.

Mike

Sorry, Steve, you should have bought a ~13 year old Accord! ;) (92 5-spd wagon, averaging over 33 overall since purchase in Feb. 36+ tootling along two lane roads at 50~60)

You might try a new O2 sensor in your Civic. I suppose it's possible that your unit is not working quite right. Check the O2 wiring connectors and harness - maybe a connection itn't quite snug. Have you looked at the plugs? They might indicate an out-of-spec mixture or other problem. Apart from that, I duunow.... Cam timing belt off a notch? Ignition timing wrong? Nerfed exhaust gasket blocking airflow? Dead squirrel in airbox?

Looking at your spreadsheet, you seem to do OK on the big road trips. What sort of highway speeds to you cuise at? If you have the time, try cutting your speed by 10KPH on your next big trip and see what happens.

As for city, just try to anticipate traffic and don't be afraid to ease off early when you see slow traffic ahead. Every time you use the brakes, you are burning gas. When accelerating, the consensus seems to be that moderate acceleration at low RPM is probably ideal. The engine will burn fuel more efficiently near 75% throttle than when tiptoeing about at 30%. (An automatic transmission may complicate things by downshifting unneccessarily.)

-Greg

I hope none of those things are wrong with my 5 month old Civic.

Steve

That's probably the answer. Civics have gained weight since 1992...

JT

And they have bigger engines, without options.

Used to be that the DX would have a tiny engine, and each level up got you into more options and a bigger motor. Now they all have the 1.6 liter, except for the Si.

You're not getting the mileage others are. Either you drive like a maniac, or there IS somthing wrong/different about your car. 5 months or 5 years, it matters not.

-Greg

He's getting similar mileage to what I am getting on the Si, which isn't good, but that could be due to a large amount of city driving or driving like a maniac.

The mileage isn't THAT far off that I would expect it to be caused by malfunction, but it is hard to tell...

Any trips that were predominately highway? At around 50-60 MPH?

The closest you'll get to EPA is usually in that range...

1.8.

I'll adjust my driving habits for a week, see what happens.

Steve

Actually, the current non-Si Civic engine is 1.8 liters; the Si engine is

2.0 liters.

The non-Si hatch engines in the 7th-gen (2001-05) Civic were 1.7 liters.