Popular Mechanics tests the efficiency of the Cobalt XFE
It seems that Popular Mechanics is nearly as interested in fuel efficiency as we are these days. To wit, the online mag has grabbed the keys to three of the latest fuel-sippers on the market in order to wring them out. The goal? Not performance, but fuel efficiency. While the Jetta TDI and the Prius are clearly the headline bearers, we shouldn't forget the lowly Chevy Cobalt XFE. This is the model that General Motors was able to massage EPA ratings of 25 miles per gallon city and 35 highway from. What's it like to drive, and does it approach those figures in the real world?
After about 500 miles of driving, PM achieved an average of 32.3 miles per gallon in combined driving. For a car costing just over $16K, that's pretty good. Remember, that number may be well below those of the Prius or Jetta TDI, but those vehicles may be priced a bit out of the range of many shoppers who'd like to save on their fuel bills. All in all, it's a pretty good effort from Chevrolet and will have to do until the Cruze arrives.
[Source: Popular Mechanics]
Reader Comments (Page 1 of 1)
as2k 3:41PM (9/25/2008)
We drove a rented Cobalt XFE from NYC to Newport and back. It was an automatic. I managed 38mpg (rated 32 hwy).
We put 1000 miles on a rented (new) automatic Focus in Oregon through the mountains and cities and averaged nearly 40mpg. In a car that goes for about the same price.
This is in rented automatics without any fancy hypermiling (aside from coasting down hills). I could have easily done over 40 with a manual. Especially the Focus, which wanted to keep the engine idle speed way up while coasting in neutral.
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MikeW 5:14PM (9/25/2008)
'Coasting' in neutral wastes gas.
nataku83 9:32AM (9/26/2008)
Last time I checked, the XFE is manual only, so you were just driving a regular base Cobalt. Still, that makes the 38 mpg even more surprising (I believe the '09 XFE is rated 37 mpg highway now).
Bill 5:51PM (9/25/2008)
I think he meant that with a manual you can cut off the engine while coasting in neutral
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as2k 6:08PM (9/25/2008)
How does coasting in neutral waste gas vs. having your foot on the pedal?
Pulse and Glide and Driving Without Brakes are two hypermiling techniques that rely on coasting in neutral (though usually in a manual transmission car).
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Pete 10:00AM (9/26/2008)
Because the calibration is set up to cut fuel with the throttle body closed and in drive. You will save more fuel lifting throttle while in drive than in neutral.
Trust me on that one.
ksmith 3:46PM (9/26/2008)
Pete speaks the truth. Coasting in gear vs. neutral will save fule b/c of the fuel cut-off.
joe cross 8:31PM (9/25/2008)
My 07 Corolla gets 36 ave. and the 09 gets 33 ave. both with a 70/30 mix of highway/city. I have a heavy right foot too.If you're not going the speed limit I'll pass soon enough.
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Noz 3:10AM (9/26/2008)
I'm curious....my Ford Focus 01 ZTS gets about 28 MPG average over 5 tanks of fuel. The best I got was 34.4 MPG going up to San Francisco or 380 miles or so.
I find it hard to believe a new Focus gets 40 MPG.
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bc 2:46PM (9/26/2008)
Different engine, different transmission, less grippy/lower rollong resistance tires...the 2009 Focus manual is rated 24/35 (unchanged from 2008). The 2001 ZTS manual was rated 25/31 at the time; estimated rating using the 2008 and later system is 22/29. I think most people now agree that the new EPA ratings are pessimistic if you pay attention to economical driving. So your 34 mpg is 17% better than the current estimate; 40 mpg on a 2009 is only 14% better than the estimate.
Luke 4:09AM (9/26/2008)
"This is the model that General Motors was able to massage EPA ratings of 25 miles per gallon city and 35 highway from."
Wrong. It gets 36 mpg highway for the 2008 model, and 37 mpg highway for the 2009 model (now on sale).
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brn 11:31AM (9/26/2008)
Noz, it's your driving. I get the same mpg as you in my V6 sedan with a 4-speed slushbox. You don't need to be a hyper miler to get pretty darned good mpg, but you do need to have a consistent mpg minded driving style.
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wild 1:03PM (9/26/2008)
Coasting in neutral saves gas in some (probably most) cars. The engine mapping of the ecu isn't aggressively tuned by the engineers to shut off the fuel to the cylinders in all cars. Since all cars are programmed differently in this regard, a blanket statement that all cars shut off fuel delivery while coasting in gear is not true. Example, the 09 Navigator has been reprogrammed to use less fuel while coasting in gear compared to the 08 model. You can look it up on autoblog.
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as2k 4:12PM (9/26/2008)
I'd agree here. It's conditional based on the car.
In the 2008 Focus I drove it made pretty much no difference in engine speed, engine braking, etc. The ECU was going to do what it was going to do regardless. For low-grade coasting it didn't make a difference. For high-grade coasting, I put it in L, the revs went up and I'm pretty sure the fuel cut off.
In the Cobalt (which I could SWEAR was an XFE, albeit an 08?) there was an obvious difference. Coasting in gear the car would slow much more rapidly than in neutral.
In a manual like my own car, coasting in neutral is much more efficient when coasting for distance/maintaining speed vs. in gear as the engine braking is strong. The fuel cutoff has an effect -- above a certain RPM. I will coast in gear to slow down or come to a stop.
Luke 4:44PM (9/26/2008)
Here are the results from my car (2005 Honda Civic non-hybrid automatic).
Regular driving: 39 mpg
Shifting into neutral when possible: 46 mpg
Engine-off coasting: 52 mpg
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wild 11:22PM (9/26/2008)
It's probably not a great idea to shift an automatic car into neutral to coast anyways. What if you mistakenly jammed it into reverse or something putting it back in gear.....ouch. Coasting should be reserved for manuals so you don't risk your transmissions existence. An automatic means that...its automatic! You shouldn't have to shift it!
In a manual coasting in gear causes engine and transmission friction, which will slow you down quickly. So even if you do save fuel in some cars by leaving it in gear, you won't be able to coast as far. So you'd have to stay on the gas longer before you can start to coast. Throwing it in neutral you can coast for a lot longer, no foot on the gas pedal a lot sooner, means less gas used. Besides, idling the engine uses an insignificant amount of fuel. So on downhills or for the last mile before your exit, throw it in neutral.
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Dave 3:20AM (9/27/2008)
Many have commented that coasting in gear is more efficient than coasting in neutral, and this is true.
But the problem is that only down steep hills are you able to coast in gear without losing speed, because you have to spin the engine. In a manual, 4cyl car at highway speeds, this means 2500-3000rpms. At least in an automatic, it will tend to let the engine RPMs fall while coasting so the engine will be spinning slower.
This is where an efficient CVT can make a huge difference in fuel economy, under very light loads where it's beneficial to spin the engine at the lowest RPM possible.
For example, on my daily commute there are a number of slight hills where I can just barely maintain highway speed while coasting. Putting the car in gear results in the car quickly slowing down.
On the other hand, our Prius is able to drop engine RPMs way down and turn off the engine (it's still turning at a low speed) and coast down the hills with no extra effort by the driver.
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Glenn 1:22PM (9/27/2008)
I'll take my Fit over this car any day. And I get 38 hwy.
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