Cars.com Mileage Challenge 3.2: The Results

Mileageday2

Yesterday, we introduced the four high-mileage commuter cars for our latest mileage challenge, which comprised about 300 miles of highways southwest of Chicago. Three of the four — the Pontiac G5, Toyota Corolla and Ford Focus — had trip computers with mpg readouts; the fourth, a Honda Civic, did not. We started the drive with full tanks of gas, logged mileage on the trip computers and calculated it again by filling up at the end of the day.

The numbers are in, and the Corolla came in first at 36.4 mpg, outperforming its 27/35 mpg city/highway ratings — and it was the only car to do so. The other three posted more modest results: The Civic (25/36 mpg city/highway) achieved 34.6 mpg, the G5 (25/37) achieved 33.1 mpg and the Focus (24/35 mpg) achieved just 31.0 mpg.

Full results below.

Mileagechart_2

As noted yesterday, we filled all four cars at one station to begin the day and another to end it, something that experts have noted could introduce slight variances due to pump calibrations. The variances should at least be consistent, however, as we filled each car from the same pump at each station. Onboard mpg readouts, which measure fuel-injector pulses (and are arguably more accurate for short-term tracking like this) indicate a closer race: The Corolla’s 34.9 mpg effectively mirrors its 35-mpg highway rating, while the G5 and Focus returned just over 33 mpg — less of a shortfall for the 35-mpg Focus than for the 37-mpg G5.

Given our fuel-friendly speeds, why did three of the four cars underperform — especially given that, in worse conditions, we outpaced the highway ratings of a Nissan Rogue and Subaru WRX? Our route was free of major elevation changes, but there were some hefty crosswinds: We drove southwest and doubled back northeast, and The Weather Channel’s weather.com pegged the northwester along our route at anywhere from 14 to 23 mph.

Turbulent air can have an effect on mileage, especially at highway speeds. According to the EPA, crosswinds introduce lateral rolling-resistance to the tires — think of the steering corrections needed to maintain a straight line — and they increase aerodynamic drag in directions a car isn’t designed to handle, both of which affect gas mileage.

Greg Fadler, an aerodynamics engineer at GM, expounded: A 14-mph crosswind on a car traveling at 55 mph can affect its drag coefficient enough to increase fuel consumption 13 percent, he said. Conversely, any sort of tailwind can help — and it doesn’t need to be coming directly from 6 o’clock. “Use a full 360-degree analogy, assuming that your nose is at 90 degrees,” Fadler said. “Zero to 180 degrees is oncoming wind, and anything from 180 to 360 degrees is going to help you.”

Given our there-and-back route, a constant crosswind from the same direction should have a zero net effect, Fadler said. The wind gusted unevenly all day — but whatever its effects, the Corolla somehow managed to fare just fine.

Mileageday21

Another phenomenon: Despite all four cars driving the same route, the G5’s odometer read 306 total miles. The others registered anywhere between 298 and 300. Asked about the variance, David DeFrain, GM’s director of infotainment telematics, said it shouldn’t be due to wheel size — the G5 XFE has 15-inchers — as the company calibrates its odometers to match a car’s specific wheels. Spokesman Tom Read added that GM tested three G5s with 15-inch wheels for odometer accuracy and found mileage discrepancies of about 1 percent, at most. Read said GM would look further at the specific hardware in our test car.

Some final food for thought: It’s possible that automatic transmissions may allow for more consistent results. Even the seasoned stick-shifters among us need a few minutes to learn the unique progressions for the clutch and gas pedal in an unfamiliar car, and over-revving the engine to ease into first or missing the timing on a downshift rev-match can take bites out of mileage. But at most, those bites were slight: The vast majority of the time in the G5 and Focus was spent in fifth gear at high speeds, a task any driver could turn into high mileage. And the well-performing WRX in our first challenge, also a stick shift, didn’t seem susceptible to any of this.

However you slice it, the G5 and Focus fell significantly short of their highway estimates. The Civic came close, but the Corolla won the day: It matched the EPA highway ratings on its mpg readout and beat them at the pump calculations. Advantage, Toyota. Stay tuned for some driving impressions and more postgame analysis.

Comments 

The Mileage on each car could attribute the the MPG's that it achieves. The last car that I bought new (03 Jetta) got between 15 and 20 miles per gallon for the first couple of tanks. My mother took it on a long drive to louisiana and back and almost immediatley It seemed to do better on gas.

These all should have been autos too.

Broq

4 different cars, 4 different drivers. Significant variation in driving style can effect results even if all drivers attempted to drive similarly.

Tire pressure - were all tires set to manufacturer specifications?

Temperature - what was the temperature during the driving as IC engines are less efficient as the temperature decreases.

Tom

Since you brought up wind resistance...how about the order in line the vehicles followed. Wouldn’t the vehicle out front encounter a stronger headwind than vehicles 2-4? Ever watch NASCAR?

I'd like to know what kind of gasoline each vehicle had, as this makes a dramatic difference for me in my vehicle. I drive a 2005 Chevrolet Malibu with the 4 cylinder and I get 39 mpg on the highway when I use gasoline with no ethanol. Whenever I have used Ethanol laced gas (10%), I experience about 5 mpg less. So I avoid Ethanol and it's funny that this never comes up.

Tom, the photos aren't indicative of the order we drove. Our cars were spread far out most of the trip, and we didn't follow any particular order, so any drafting effects should be minimal.

Second commenter: If you read the post, you'd see your questions answered. Temps ranged from 41 to 52 degrees Fahrenheit; we switched drivers three times so each car had a roughly equal share of different driving styles; and we filled cold-tire pressure to manufacturer specifications at the beginning of the day.

Kelsey

Bloke

There will always be naysayers and those who just won't accept that their car doesn't get 40 miles to the gallon. I trust the authors have some experience conducting experiments and kept the proper controls and variables. I am going to give them the benefit of the doubt that they followed the manufacturers recommendations about driving the vehicle to achieve maximum economy. What worries me most is how the EPA estimates appear to be so far off for the American makes.

Tony

If the test was done as described - it is clear that Honda and Toyota again proved to be better for consumer then American makes because they were clear on the mileage while Ford and GM again posted bogus numbers

Bloke

Ford and GM do not post there own numbers, those are the EPA numbers.

Tony,
Why don't you base your comments on factual information. You and everyone else knows that manufacturers post fuel economy estimates from EPA testing, not internal testing set up to dupe customers. And you and everyone else know they are estimates only.

Tony

Before nameless and other here will kill me...

From the EPA website:

"All new cars and light trucks sold in the U.S. are required to have a economy label posted on the window sticker. The label contains the city and highway miles-per-gallon values, as well as other related information. To calculate these values, laboratory tests are performed on pre-production vehicles. Most testing is performed by manufacturers at their own testing facilities. EPA audits the data from this testing and performs its own testing on some of these vehicles to confirm the manufacturers' results..."

Notice: "Pre-production vehicles" and "Most testing is performed by manufacturers at their own testing facilities".

Conclusion:
There are still plenty of strings in the hands of manufacturer and plenty of opportunity for fraud.

Bloke

Hah-Hah! Good showing, Tony. But I would hope that the EPA went over the tests for these vehicles especially since they just revised the calculations. Claiming class leading mileage is a big marketing plus right about now.

Probably a result of some government cut-back...

GR

I would think the trip computer readings would be the ones to compare and at that, they are within one to two miles per gallon of one another. That's not so bad. Too bad the Civic didn't have a trip computer. Actually, for the price, I'm surprised it doesn't. The pump fill up method is not exactly accurate but good for general use.

Notice: "EPA audits the data from this testing"

Conclusion: There is a huge conspiracy going on between car manufacturers and the EPA and Tony has proven it.

It's not that automakers would lie about their EPA numbers, but gearing and other factors could be designed specifically to fit the standardized test.

The results are fine by me - our 3400-lb. Milan gets 35-40mpg on the highway (rated at 29), and that's with 10% Ethanol in our gasoline.

I'm thinking it's those crosswinds at work, when you're on the highway, it really will take an unbelievable amount off your fuel economy in order to maintain a steady speed.

J

Geez, the first leg was avg 62mph, are you guys racing?

Idaho Guy

Guys, please add the Korean variants in your next test. I think you are doing them, and us, an injustice by their omission. I'm regularly getting 33-36 in mixed driving in my manual transmission '07 Spectra. Best value out there in terms of cost/mpg's.

If you consider that the average freeway/highway speed is 65 mph, an average of 62 mph is normal...

Jason2

I notice you did not drive the cars at the same average speed. Now, not being a mathematician nor an engineer, I don't know what is an acceptable range and how it affects the results. Here is the overall average speed of each vehicle:

Focus: 53.75
Civic: 54.00
G5: 54.75
Corolla: 53.50

So, is this an acceptable range? I am not trying to make the American made cars look better, I am just wondering since they did not keep all the vehicles at the same speed, apparently. Was cruise control used during any of the testing?

sheth

even though the G5 was lower than EPA estimates it should be noted that it has the more powerful engine by a significant margin. 33mpg for a car with 155hp and 150 lb-ft is very respectable. The G5 is likely the fastest car in this bunch with a 0-60 time under 8 secs. The others are likely in the 9-10sec range. You give up a couple of mpgs and you gain passing power.

Bloke

The whole point of the challenge was mileage not speed. The acceleration times is irrelevant.

Bloke

I think the use of cruise control could be an important factor though.

Guys, check out the first post:
http://blogs.cars.com/kickingtires/2008/11/mileage-blog-1.html

It details the parameters we followed. Suffice it to say we didn't use A/C or cruise control, kept the windows and sunroofs shut, filled tire pressure to the MFR recommendations at the beginning of the day and rotated drivers throughout the drive.

Kelsey

J

Bloke,

Cruise control actually does not help mileage when comparing to a steady right foot unless it is on open flat road.

Maybe so but not everybody has a steady foot. In a test like this, using cruise control would have minimized variation even further than not using cruise control. This test was a comparison of vehicles and not an attempt at maximum fuel efficiency.

J

But with a driver being a variable, how can we say the test is legit?

Because they rotated drivers for equal time in each vehicle.

Bob

Sometimes I wonder what is wrong with these new cars. I drive 3 hours each way 3 days a week in my 2001 Grand Am 2.4 automatic, and pull atleast 36 mpg. That is on a bad day, and going 72. I bought the car 2 years ago with 24k miles on it, it now has 148,400 miles. So if a car that old with that many miles can do that good why, cant a new car designed to do good do any better? I mean come on, my car is rated at 29mpg on the old system, and still exceeds that easily. Why cant these new cars atleast meet there ratings?

Bob

Sometimes I wonder what is wrong with these new cars. I drive 3 hours each way 3 days a week in my 2001 Grand Am 2.4 automatic, and pull atleast 36 mpg. That is on a bad day, and going 72. I bought the car 2 years ago with 24k miles on it, it now has 148,400 miles. So if a car that old with that many miles can do that good why, cant a new car designed to do good do any better? I mean come on, my car is rated at 29mpg on the old system, and still exceeds that easily. Why cant these new cars atleast meet there ratings?

Bloke

J, cruise control will moderate the fuel to engine to maintain the same speed more effectively than your own foot will. If you are willing to go up a hill slowly instead of with the cruise control on maybe, but tell me where you did your scientific tests? On the same run where you got 40 mpg in purely city driving in a non-hybrid?

ttc

Only 31 MPG overall for primarily highway driving in the Focus? I drive an '09 Focus SEL 5MT (with 16" wheels/tires and the same gear and final drive ratios as your '08 SES tester), and have handily exceeded 31 MPG overall with a 55% highway/45% arterial and local route allocation. Heck even Consumer Reports got 29 MPG in a 5MT Focus with an even more stop and go oriented driving schedule.

The Focus has an upshift indicator light (I think the G5 does as well). Did your drivers obey it?

ttc

To the poster who stated "IC engines are less efficient as the temperature decreases": that assertion is incorrect.

Lower ambient temperatues are associated with GREATER thermal efficiency of internal combustion engines. However, longer warmup times & idling, increased tire rolling resistance and air drag often negate that advantage in actual driving.

Learn to read folks:
"Greg Fadler, an aerodynamics engineer at GM, expounded: A 14-mph crosswind on a car traveling at 55 mph can affect its drag coefficient enough to increase fuel consumption 13 percent, he said."

Whooo

Yeah and then there is "Given our there-and-back route, a constant crosswind from the same direction should have a zero net effect, Fadler said."

To ttc: I was referring to fuel efficiency, not thermal efficiency. The air/fuel mixture is richened until the engine gets up to operating temperature and then it takes extra fuel (energy) to keep the engine at an efficient operating temperature.

Above, you just said the exact same thing ttc said. And anyway, cold air is used for a more dense fuel charge, hence cold air intakes. This increases fuel economy.

^^^Really? How about reading the two again. And explain to me the myth of increased fuel efficiency with a cold air intake?

Just read it. You're saying their needs to be more energy to keep the engine warm. And he is saying lower temp are more efficient. You are disputing the same thing. You can read it as many times as you want. How is it a myth? You've never heard of getting better mileage with an intake? Get off this website you maroon.

More on that myth about cold ari intakes

Even so, our sources saw significant opportunities still available with cold-air intakes. Despite the technology and warranty issues, consumers continue to see intakes as easy bolt-on products, and the recent spikes in fuel prices offer another marketing approach. Cold-air intakes do provide fuel-economy increases, though they might be mitigated by the consumers more aggressive driving habits after a cold-air intake installation.

This is from SEMA, I think they know something about cars.

It's "moron" by the way, not "maroon". ttc is correct in that the theoretical thermal efficiency of an engine is higher with a higher difference in temperatures. The combustion temperature is going to be the same and the ambient air temperature is the variable. Lower ambient air temperature means higher thermal efficiency. While the thermal efficiency may be higher, I am saying the fuel efficiency decreases for the reasons I stated earlier. And the cold air intake is a myth if you think it decreases fuel consumption which is why I asked you to explain it to me. Give me a substantiated explanation and I will believe you.

Sorry, my vocab can be a little outdated sometimes. Maroon - a person who is stranded, meaning you have no hope, you make this apparent with your last post. Just keeping saying thermal efficiency, you still don't know what it means. You said cars get worse mileage when it is cold outside, you didn't give any reasons. You are wrong, if the air is cold you get better fuel economy - hence cold air intakes.

Ooops, I see it now. You said a car uses more in gas to keep itself warm. YEAH! Once that engine block heats up it is staying there, the explosive force of gasoline drives the car, not the heat that is generated.

Thanks for all your intelligent responses. Come back when you can explain it with a little less name-calling and a little more physics.

Sorry, but it doesn't take physics to see this stuff. I don't think you or I really understand physics. I am only going off of what experts say. They have already done the physics.

But anyway, how does it feel to be dominated?

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