Honda Civic mpg

I’ve been thinking about purchasing a new Honda Civic. I haven’t yet decided whether I prefer a manual or automatic transmission. In the past I’ve opted for manuals primarily because they have traditionally produced somewhat better gas mileage. However, with the new Civic there is some confusion on this. On their website Honda reports the following for the Civic: Manual 26/34/29; automatic 25/36/29

I don’t understand how the automatic can be rated higher for the highway estimate (36) than the manual. Is this information accurate? To confound matters, Consumer Reports April 2008 on p. 32 indicates that the overall mpg for the Civic manual is 31 and the automatic 28. This would seem to me to be consistent with the traditional differences between manual and automatic. Honda’s website, however, reports 29 mpg for both the manual and automatic in overall mileage. There seem to be some inconsistencies. I would like to know what others think.

When in doubt, believe Consumer Reports; they do real world tests, and their conbined MPG represents what you would normally get. The Honda figures are likely combined city and highway EPA figures, achieved IN A LABORATORY SIMULATION as per the mandated test. Those figures are normally with the A/C off.

In summary, you will likely achieve close to the CR figures, and maybe a little bit better when the car is properly broken in.

The reason why a manual traditionally gets better mileage is that the engine is directly coupled with the transmission-- with an automatic, the torque convertor causes slippage that wastes some energy and results in lower gas mileage. On newer automatics, however, the torque converter can lock-up, directly coupling the transmission to the engine at highway speeds. Add to this that carmakers put a lot more R&D dollars into automatics than manuals, which leads to the automatics being better geared or otherwise more advanced than the manuals-- hence the better mileage.

The gearing is different for both the transmissions and drive axles. The final drive axle ratio for the automatic is 4.44:1; it is 4.29:1 for the manual. But 5th gear is 0.53:1 for the automatic and 0.73:1 for the manual. If you multiply the two respective ratios together you get the overall reduction of engine revolutions to wheel revolutions. It’s 2.35:1 for the automatic and 3.13:1 for the manual. This means that the engine rotates 2.35 times for each wheel revolution in the automatic and 3.13 times for the manual. That explains why the highway mileage is better for the automatic, since you are in 5th gear most of the time. It’s not that simple for city driving, since you aren’t in 5th gear much of the time. The current EPA estimate for manual is 26/34 and 25/36 for automatic.

The car is set up according to the demands of the customer (average). Most people that want a manual want it to be peppy, hense the different gear ratios.

EPA MPG figures are generated as a by-product of emissions testing and are precise, for the drive cycle used for this test. They are excellent for comparing one car to another, since the same cycle is used for all vehicles. It is somewhat less strenous than normal driving, hense the higher numbers than most people get in the real world. Automakers have been known to design around the test-to maximize mileage-for obvious reasons.

There are many differences in the way the cars are built. The posters are right about the gear ratios and things like that. The people who test the mileage just put the results on the paper. They get what the car gets. Consumer Reports does better testing.

Check out for owner reports. Look for a significant number of reports (not just 6-7, but closer to 20 or more), then look at that data. That’s probably the best real-world results you can get, even better than Consumer Reports.

Those mileage numbers are essentially identical, just buy whichever type you prefer to drive.

I would tend to agrre with Craig that the mpg results are virtually the same for each car. Fuel economy should not be a deciding factor in choosing the type of transmission for your new Civic.

This makes a lot of sense. Thanks!

Consumers Reports may have bought one of each for their testing or used reader inputs, I didn’t read the article so I don’t know which. Also, they may have been comparing different years because they seldom check a manual vs. automatic at the same time. Either way, when you are using only one of each, there will be differences due to manufacturing variances.

Over all, both Honda and Consumers Reports do try to keep the variations to a minimum and CR does say when that the differences are statistically insignificant.

Since the cars are theoretically able to attain nearly identical fuel economy under ideal conditions, the biggest difference in the real world will be your right foot. Buy whichever one you like best.