I've wasted countless hours searching for an answer to this question. So I've finally decided to make a post.

What exactly is the difference between the Sport AT and the base AT that causes the difference in EPA estimates mileage?

Is it different gear ratios? I've heard this hypothesis on the forums, but it appears from Honda's website that the gear ratios are the same.
Is it the difference in weight and wheels? Unlikely because Sport MT and base MT get the same estimates.
[Update (3/27/09): Perhaps people (myself included) have incorrectly assumed that Sport MT and base MT really would get the same numbers number EPA testing. Instead, my hypothesis is that Honda reported the base MT EPA MPG numbers for both the base MT and the Sport MT. EPA considers the Sport MT and the base MT to be similar enough that it allows such a practice. However, when it comes to the Sport AT vs base AT, because of the ostensibly different transmission, EPA requires separate testing on the Sport trim. This hypothesis is supported by the fact that fueleconomy.gov has only three entries for the 2009 Fit: manual, normal AT (base AT), 2mode AT (Sport AT).
We may further conjecture that if the sport MT were put through the same test, its MPG estimates would similarly be slightly worse than the base MT MPG estimates.]
[Update (3/27/09):
Curb weight is not the primary reason for the difference in EPA estimated MPG between the Sport AT and the base AT, because according to Honda website, the difference in weight is less than 30 pounds. The difference between 33 MPG (sport AT EPA highway) and 35 MPG (base AT EPA highway) is 6%. It is extremely unlikely that a 30 pound difference in a 2600 pound car changes fuel economy by 6%. Furthermore, it has been pointed out that a higher speeds that is typical of EPA highway tests, weight makes comparatively little difference because most of the energy is expended to overcome aerodynamic drag.
Drag is a factor I neglected to mention before. But now it appears to be the most likely reason for the difference in EPA estimated MPG between the Sport AT and the base AT. Does anyone have numbers that compare the drag coefficient and area of the sport Fit vs the base Fit?
The different wheels may also be a factor. The base has smaller and heavier wheels compared to the Sport which has larger and light wheels. It is unclear which one would have lower rotational inertia. Does anyone have numbers?]

Is it the difference in shifting pattern? I've read magazines and reviews say that Sport AT uses a more aggresive shift pattern than base AT, ie. it downshifts more and upshifts later.
* Has this been verified?
* Is there any more information on just how the patterns are different? e.g. late 4-5 shift but everything else the same.
* I presume the difference is in comparing D-mode to D-mode, not S-mode to D-mode. It would be pretty stupid for Honda to do EPA testing using S-mode without paddle input. Can anyone confirm?
* Why would Honda make the D-mode behave differently in Sport and base and lose 2MPG highway on the sticker? It seems like they could have the cake and eat it too by optimizing D-mode for fuel efficiency while touting the S-mode for aggressive driving.
* If the difference is strictly shifting pattern, then in theory, one could use S-mode and paddle inputs to simulate the base AT shifting pattern and get the same mileage?

Some information I've gathered:
EPA mileage according to Honda [city/highway/combined]:
Fit Sport AT: 27/33/30
Fit base AT: 28/35/31

Fit Sport MT: 27/33/29
Fit base MT: 27/33/29

EPA mileage according to fueleconomy.gov [city/highway/combined]:
2009 Fit Automatic (L5), CLKUP: 28/35/31
2009 Fit Automatic (S5), 2MODE CLKUP: 27/33/30

So it appears that Sport AT corresponds to S5 and base AT corresponds to L5.
S5 means semi-automatic 5 speed. L5 means automatic 5 speed with lockup.

According to Honda's 2009 Fit specification page:
On both sport and base,
5-Speed Manual Transmission Gear Ratios: 1st: 3.308, 2nd: 1.870, 3rd: 1.303, 4th: 0.949, 5th: 0.727, Reverse: 3.308, Final Drive: 4.62
5-Speed Automatic Transmission Gear Ratios: 1st: 2.996, 2nd: 1.679, 3rd: 1.067, 4th: 0.761, 5th: 0.552, Reverse: 1.957, Final Drive: 4.56

 

the body kit on the sport along with the wheels make it get
worse gas milage. thats pretty much it.
also the base has no paddle shift and the sport does.

IMHO one miles per gallon is not going to make me buy a base.
the sport is way better equiped. and way better looking.


FYI i have a sport auto and i get 40MPG.

 

Thanks niko. But I don't think that's it. As I mentioned in my original post, the Sport MT and the base MT get exactly the same EPA estimated mileage. If it really is the body kit and the larger diameter wheels that made the difference, wouldn't the same difference be there between the Sport MT and the base MT?

 

The difference is how the AT handles the extra weight (suspension etc.) and different tires with the Sport trim. It might have to shift slightly differently to account for wind resistance with the added weight. Simple as that. Those 2 mpg should not even be close to a deal breaker for the added benefits of Sport.

 

A portion of the difference could be in the roundoffs: 27.4 -- goes to 27; 27.6 -- goes to 28. However, it is a bit mystifying. Slight differences in the computer-controlled shift points may result in measurable differences when the rules and protocols of the EPA's stop and go cycle, or highway cycle are rigidly imposed. In the real world, I would bet that the differences are quite small, and attributable to slight different friction from the tires, and differences in aerodynamic drag.

 

I will be honest, one of the reasons I wanted base over sport was because of the MPG difference. 2 MPG can add up for me since I drive 50 miles a day for work. But it wasn't the only reason. Sometimes I think about how maybe I should have got the sport but then I always come back to my list of reasons for getting base and I am okay with it. If you like the sport better and the only reason you are considering base is because of the MPGs, you should go probably go with the sport. Espessially since many are getting well above the reported 33 MPG.

 

Thanks, Minnemike. Just to be clear, I am already a happy owner of a GE08 Fit Sport AT (since 10/10/2008). This discussion is not meant to inform my purchasing decision.

So you're saying that the AT is not programmed differently, but simply behave differently due to different conditions (weight, rotational inertia of wheels, drag, etc).

But if this were the case, I still think we should see a similar difference between the sport MT and the base MT.

Actually this lead me to a new hypothesis. There IS a similar difference between the sport MT and the base MT. It's just that EPA does not mandate separate testing for the two because they have exactly the same gearbox setup! So Honda is able to report the base MT EPA MPG numbers for their sport MT as well! Any thoughts on this hypothesis? (I'll update the original post to include this new hypothesis.)

 

easy... tire size and weight difference.

 

Thanks, kenchan.
The wheel difference is plausible. The sport has larger wheels (but also lighter due to use of alloys vs steel). Larger wheels would tend to have higher rotational inertia (bad for MPG), but lighter wheels would tend to have lower rotational inertia (good for MPG). Do you have any data that shows the alloy wheels in the sport trim have higher rotational inertia than the steel wheels in the base trim?

Though the curb weight difference is not very plausible. As I wrote in an update to the original post, the 30lb (1%) difference in curb weight is very unlikely to cause a 2MPG (6%) difference in EPA estimated highway fuel economy. Do you agree?

 

Absolutely right!

 

Ah. When you said tire size I assumed you meant wheel size. So I started thinking about rotational inertia of the wheels.
But now I think you meant tire size as in the wider tires (185mm on the sport vs 175mm on the base) having more rolling resistance and more aerodynamic drag?

 

epa mpg can be beat by far,if you have a light foot.
i have a mt sport,trip 95% 64 mph on interstate,45/50 mph
on backroads.
398 mi 8.305 gal's fill up same gas station,same pump, same direction.

 

You could be exactly right... it makes sense anyhow - if they simply consider the Sport trim parts to be merely add on components and not requiring a different test.

I was thinking that sport AT may be programmed differently with sport mode too. So both weight and programming with sport AT vs. base AT being the variance. Also... with MT, would results be more normalized due to the driver's influence in shifting and feel? Not really sure how these EPA test are actually conducted.

 

TCMIV, I was wondering about this same issue and it seems to be widely misunderstood.
What conclusion did you come to eventually to explain the official FE ratings discrepancies?

I always assumed that if there was a difference between sport MT and Base MT, then it would have been explained by wheel weight and tire width. Would love to know THE WEIGHTS for both setups (stock steel, vs stock alloy in 16 inch dia).

The side skirts, and rear wing may be affecting the coefficient of drag, but I actually remember reading that rear wing would help smoth out the turbulences.

Please share your updated conclusion.

 

Honda says the Sport with automatic is lower than the base model due to some engine tweaks aimed at better throttle response, increased aerodynamic drag of the spoilers, and increased rolling resistance of the wider tires.

Go to: 2009 Honda Fit: Deep Drive - Consumer Guide Automotive

and scroll down 2/3 of the page to Fuel economy .

 

My best has been 47 mpg (hwy at 53mph) i average 41-43 mpg mixed 2009 fit sport 5 speed w/ a k&n stock replacement filter