Why Do Subcompacts and Compacts Get Such Similar Mileage?

2012hyundaiaccent
No longer is 40 mpg only the province of the hybrid.

With four new members from the New York International Auto Show — the Honda Civic, Hyundai Accent, Kia Rio and Mazda3 — the crop of 40-plus mpg, non-hybrid gasoline cars available will creep into the double digits by the end of the year. You don’t necessarily have to downsize to get the best mileage: The 2012 Ford Focus SFE will be rated 28/40 mpg city/highway, while the pint-sized Ford Fiesta SFE gets 29/40 mpg. The entry-level Accent gets 30/40 mpg; the Elantra, its larger sibling, is rated 29/40 mpg. The stick-shift Chevy Cruze Eco gets 28/42 mpg, and GM expects the forthcoming Sonic to secure a 40 mpg highway rating.

In most cases, the compact cars are significantly larger, heavier and more powerful than their subcompact siblings. Why then is their gas mileage so similar? At the auto show, I posed the question to automakers and analysts. The simple answer: aerodynamics.

“Keep in mind that technology will help both [highway and city mileage], but not at the same rates,” said Mike O’Brien, Hyundai’s vice president of product planning. “The city number is going to be the bigger difference when you go a class up in car size.”

Conversely, the fight for better highway mileage goes against what O’Brien calls “road load,” a combination of the vehicle’s frontal size, tire friction and drag.

In some cases, it’s actually harder to eke out better highway mileage in a subcompact car, said IHS Global Insight analyst Aaron Bragman.

“When you have a B-segment [subcompact] car, it’s very hard to make it aerodynamic, given how short it is and how many of them end abruptly,” Bragman said.

That’s not to say carmakers aren’t trying. Cars like the Accent and Fiesta use technologies commonly reserved for luxury models — a direct-injection engine in the Accent’s case and a dual-clutch six-speed automatic in the Fiesta’s.

At Ford’s auto-show stand, marketing manager Robert Parker noted the incremental nature of this technology.

“Our engineers like to say fuel economy is about hundreds of little things,” Parker said. “All of those hundreds of little things add up to a tenth [of a mpg] here and a tenth there.”

Put another way, major increases in mileage — 30-mpg pickup trucks or 50-mpg commuter cars — will take more than slipstream aerodynamics or six-speed automatics.

“A lot of these countermeasures are low-hanging fruit,” Bragman said. “Long-term, you’re looking at a different powertrain, a different type of propulsion method, to get to the next level of fuel economy.”

The real question isn’t technology, Hyundai’s O’Brien said. “There’s always more technology,” he said. The real question is who will pay for it.

“You can have the cleanest car in the world, but unless someone buys it, you can’t be clean,” he said. “It’s really a tipping-point discussion.”

Comments 

Rockaby

The real question isn’t technology, Hyundai’s O’Brien said. “There’s always more technology,” he said. The real question is who will pay for it.

“You can have the cleanest car in the world, but unless someone buys it, you can’t be clean,” he said. “It’s really a tipping-point discussion.”


Thank you. I've said that for years. I've said "I firmly believe that there is the technology out there today to get 50, 60, who knows how many mpg...but I bet the engine/transmission alone will cost way too much that it will scare people away."

But as far as today goes, it's interesting to hear that about the aero and stuff...I want to know why Hyundai still has the Accent around since it's barely any better than the Elantra in fuel economy, only 5 inches shorter in length, and almost the same price when comparably equipped.

Lance

They mention that the big difference is in city MPG but then cite examples that are about one MPG apart. That's a big difference? I can see aerodynamics being a big factor at speed but you would think the city MPGs would be better on the subcompacts.

Rockaby

Lance,

your post continues my questioning of why the Accent exists. However, you can see a huge city difference between the Sonata (22/35) and the Elantra (29/40) which is an improvement of 32% in the city and 14% on the highway

Rockaby,
Good question regarding Accent/Elantra. I suspect weight plays a major role. Comparing automatics to automatics, the two sedans are only about 250 pounds apart — less than the average difference between a Ford Fiesta and 2012 Focus (318 pounds) or a Toyota Corolla and Yaris (421 pounds).

Incidentally, the Accent has a direct-injection four-cylinder; the Elantra's is port-injected. In our interview, Bragman went on to note that the limiting factor on the Accent is how short it is. The longer Elantra is more aerodynamic (.28 cD vs. .30 cD) and Bragman expects it to get *better* EPA ratings than the Accent once Hyundai adds DI to its powertrain. All of that goes to show how important aerodynamics are, especially if vehicle weights are in the same ballpark.

Kelsey

JM

the Accent is there for the base model that costs much lower than the Elantra. believe it or not, but people actually do still buy completely stripped cars if they need a set of cheap wheels.

Rockaby

JM,

Why couldn't the Accent be killed off and the Elantra just be given an even more basic model?

Collision of Souls

The Accent is direct-inject and and 1.6 displacement with 138 hp and 40 mpg. The Elantra is NOT direct-inject (yet) a 1.8 displacement , 148 hp and 40 mpg.

The Elantra will do even better when they upgrade that engine to direct-inject.

I think the 1.6 engine in the Accent is very capable and efficient. They have 1.4 engines and smaller but they wouldn't have the hp North Americans like.

www.isleofexile.blogspot.com

Mark of Excellence

Subcompact vs. compact is just a marketing decision. Fiesta, Accent, Sonic and others of that ilk aren't needed in the US when you have Focus, Elantra, etc, all of which get the same or better mileage. In third world countries the small cars are offered with smaller engines that are slow, but get super mileage. In those markets the differentiation makes sense.

FlanKitty

the other part of "who's paying for it" comes in the form of the lack of margins in B-segment cars in many markets.

it's fairly easy to eek out fuel efficiency by making the A/C, oil and coolant pumps run off electricity (vs drive belt) but unless there is a market for premium compacts, the cheaper parts list gets the sell.

cody

what they need to do is bring the smaller engines from the other markets to the u.s. with DI so that the engines make around 100hp. that's what sub-compacts used to produce, and the results were high fuel economy. in most cases, it's either power or fuel economy, not both.

Troy S.

I agree Cody. Manufacturers like Ford have taken your idea of importing the engines to a different level. They're importing their overseas cars. The Fiesta is an example.

Mark of Excellence

Cody and Troy,
I'd like to see a 1.1 litre, turbocharged Fiesta sold in the US. It would get 40 mpg in the city and 50 on the highway. Considering Ford will incorporate stop start technology to all of its cars by 2013, such a Fiesta might do better.

Tom

My 12 year old Saturn gets the same mileage as these new cars (29/40). And my previous car, a 1985 Grand Am, was getting great mileage before that (27/35).
There has been little change in the efficiency of automobiles in the last 25 years.
The cost of building the engine/drivetrain isn't the problem. It's the push for bigger, faster cars with consumers not as interested in efficiency that is the problem.

cody

Mark,

that would be a great model to bring to the U.S. if it were turned for efficiency instead of 0-60 times, it would create the separation between sub-compacts and compacts that used to exist.

Tom,

you're absolutely right about fuel economy not improving. it's primarily due to all of the technological engine advances over the last decade (until recently) being applied toward getting more power out of the engines instead of using them to provide the same power on less fuel. of course, part of that was necessitated by weight gain...but part of it was because every car produced today has to outrun an 1990s mustang or camaro.

Please look at my invention that makes small cars safer in collisions.
www.safersmallcars.com
On the website, you will see how I propose to lengthen the wheelbase of a short city car to give it a better ride. The extra length can be used to make it more aerodynamic.

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