Just as vehicle line director Tony Posawatz was asked by Fox the other day, Lutz was also asked what the Chevy Volt’s MPG will be when it is running in charge-sustaining mode, after the first 40 all-electric miles have been driven.

As someone who has followed this Volt story since day one, along with many of you, I have found that Bob Lutz cannot help but be honest.  GM has never officially acknowledged this number though at the time of the initial concept revelation they mentioned 50 MPG was the goal.  However, in those days the generator was to be a 1 L turbocharged 3 Cylinder, and not the normally aspired 1.4L 4 cylinder it turned out to be.

When now asked what the Volt’s fuel economy would be in charge sustaining mode, Lutz replied as follows:

We haven’t published it and it’s not finalized.  Once it’s running on pure gasoline it will be like a highly economical vehicle in that size class. It will be exceptionally good mileage but it obviously won’t be comparable to what it is when it runs on electric.

The vehicle is conceived primarily for urban or suburban use. It’s for that 80 percent of Americans who travel 40 miles or less per day; they will never use a drop of fuel.  If you have a 60 mile commute, you’ll have 40 miles purely electric, the remainder of the mileage on very good gasoline mileage, and your average fuel economy will be somewhere between 120 and 150 miles per gallon.

So let’s do the math.

On a 60 mile commute, the first 40 miles are electric and the next 20 are on gasoline.  At an average of 120 mpg, that would mean 0.5 gallons are used in those 20 miles (40 mpg).  At 150 mpg, it would mean 0.4 gallons are used in those 20 miles (50 mpg).

Thus the Volt will average between 40 and 50 mpg in charge sustaining mode.  Good enough for me, how about you?

Thanks to Philerup for the tip!

When the Volt concept was first unveiled math models put it at 50 MPG, however since development began in earnest GM has kept silent about what it is actually turning out to be.  The only thing everyone has heard by now is that city drivers could expect an average of 230 miles driven for every gallon of gas used over time, assuming a daily full charge.

However, when going on road trips for distances significantly greater than 40 miles it is still important to know how much gas the Volt will use in that setting.

The last time I asked Volt engineer Andrew Farah this question he said the MPG will “not significantly” differ from 50 MPG.

When we ran a poll on the topic here in August, 58% of 1549 voters predicted it would be less than 50 MPG, with the majority choosing 40 to 50 MPG range.

The question was recently asked of Tony Posawatz, Volt vehicle line director, by a Fox news reporter who actually had a good understanding of the car’s engineering.  The video of this interview at the bottom of the post is well worth viewing.

When asked what the Volt’s MPG will be in charge sustaining mode Posawatz responded:

“We’re still testing that in all honesty, but we can make the following statement. It will be better than any conventional car in the class and we’re trying to figure out how close or if it will be actually better than other hybrids.”

According to fueleconomy.gov, the car with the best fuel economy in the small car class is the Toyota Yaris which gets 29 MPG city and 36 MPG highway for a combined fuel economy of 32 MPG.

Though Fox as a result of the interview reports“Chevy Volt to Get 32 MPG?” Posawatz seems to clearly state it will be more than that.

Clearly there will be an effect.  During the recent 30 to 40 degree mornings I, for example, have been driving my MINI E electric car with the heat on moderately for the first time since I got the car in June.  This is resulting in around a 10 to 15% decrease in range.

Conventional gas cars are able to use the heat of the gas engine to heat the car but pure electric cars and the Volt in EV mode don’t have that luxury instead having to rely on electric heating elements.

Indeed GM announced in August that using some unspecified average amount of HVAC and city driving schedule, the Volt would achieve 25 kWH/100 miles.

As was reported yesterday, a fleet of eight integration Volts are currently on a three day extended test drive which will total 1200 miles of driving.

Among many other things, engineers have been testing the HVAC and Volt engineer Andrew Farah explains how the Volt will handle this issue when he was asked how HVAC draw will affect range.

There is going to be an effect , there is no question about it. What we’re trying to do is give the customer an opportunity to decide how much they want it to have an effect.

For example, one of the things that the Volt has that other cars don’t is not only do you select what temperature you want and things like that, but you can also select if you want it to use full available power because you’re interested in being 100% comfortable 100% of the time, or whether or not you want to restrict how much power the system can use.  Yes that will take a little longer to heat or cool the cabin, but again it really has to do with what the customer is interested in doing. We try to make it easy for them to make that kind of choice.

So it seems the Volt will let you dial in an economy HVAC option to extend your EV range if desired.  It is also believed that the Volt will be able to programmably precondition the temperature of its cabin while plugged-in, using grid energy, therefore requiring less energy from the battery once driving begins.

So what are the priorities of we early adopters?  Will you choose to limit your HVAC power to extend range, or just go for sheer comfort?
Note: There is a poll embedded within this post, please visit the site to participate in this post's poll.

We understand a lot of information will be available on those displays, they are configurable, and the driver will be able to choose among many options.

A primary function will be to provide the driver with feedback on how fuel efficient he/she is driving and utilizing accessory loads such as HVAC.

As anyone who like to hypermile hybrids knows, seeing real-time instantaneous MPG is a useful measure to adjust driving behavior as one moves along varying road conditions.

I asked Tony Posawatz who is the Volt vehicle line engineer if that value will be provided while the car is running in charge-sustaining (generator) mode.

“I don’t think we will show instantaneous mpg,” he said. “We are working a lot on what information to show and how to present it right now.”

“The OnStar capabilities with VOLT will be mind boggling,” he said. “Stay tuned.”

I would imagine driving style will affect the Volts’ electric range. Hyper-milers probably will try to get the car to go 100 miles without going into generator mode.
Yes. I can probably get it to do several hundred miles downhill with tailwind. To be honest with you there’s several driver interfaces that try to teach drivers. We’ve not talked too much about the man-machine interface, but it will have the necessary tools to allow drivers to modify their behavior for maximum electric range.

Will you have an interface like Ford or Honda that show these green leaves and things?
The Volt will have a very cool set of graphic interfaces for the drivers. We’ve got two different reconfigurable display areas, a primary right in front of the driver where the traditional cluster is and a secondary at the top of the center stack that will have content unique for a driver interfacing with an electric vehicle.

You haven’t shared what that’s going to look like yet.
No but it’s very well done. It’s very impressive.

Very similar to the charge sustaining story, ongoing refinement. While we have time were going to make it perfect. All the fundamental basic functions are already done, we’re making it perfect, cool, and sexy.

Some of these schedules that some of these companies make when they say they get hundreds of miles of electric range, the schedule that you’re on can help influence that.  In the Volt if you do 35 mph flat terrain steady state there’s upside potential over the 40 mile range. One thing we’ve got to look out for is that the US consumer is not happy with the EPA mpg ratings in that they don’t necessarily represent real world driving conditions. We’re being very careful to not allow the perception to exceed the reality. You don’t want to overpromise and underdeliver

It seems to me you feel you are going to underpromise and overdeliver?
That’s fair. Were being somewhat conservative again because we want to be successful with the technology.

Although the Karma shares the same general engineering architecture as the Volt, the similarities end there. The car will have a 50 mile range in EV mode using 22 kwh of lithium-ion battery storage and after that a charge-sustaining mode with generated by a 260 hp GM Ecotec 2 liter engine.  Fisker has not announced the total capacity of the battery pack.

The dramatically-styled sports car has up to 405 horsepower, 959 lb-ft of torque, and can do 0 to 60 in under 6 seconds. It will retail for $87,500.

As the Volt 230 MPG announcement drew a lot of attention to it, Fisker too has decided to announced some numbers of its own.

Using the European format they claim the car will emit 83g CO₂/km (less than the Prius’ 87 g CO2/km₎ and will have a fuel economy rating of 3.5L/100km.   This translates to 67.2 MPG.

The Karma is configured to operate in what they call stealth mode (EV mode) that the driver can activate via a steering wheel mounted switch, or in sports mode which uses the gas generator continuously.  The car’s default operation will be EV for the first 50 miles switching to generator after that.  The car will have less performance in stealth mode, topping out at 95MPH (down from 125 MPH) and doing 0 to 60 in 7 seconds.

According to Fisker spokesperson Russel Datz, the announced 67 mpg number is combined city and highway, and was arrived at using the SAE J1711 standard and the SAE J2841 standard which takes population behavior (utility factor) and nightly charging but not petroleum equivalence of electricity into account. Electric usage will be reported separately.

In the case of the Volt, the 230 MPG was determined by measuring the average driving behavior of a typical population who would be recharging nightly, and seeing how many city miles they would accumulate while burning one gallon of gas.  Highway and combined numbers were not released.

Datz said in city driving, the Karma would be rated around 150 MPG.  Similar to GM, he wouldn’t not disclose the MPG of the Karma in charge sustaining mode.

Per Fisker’s press release:

Fueling the Karma could cost just 0.02 euro/km ($0.03/mile), consuming as little as 21 kilowatt hours per 100km in its electric-only Stealth mode, according to SAE methodology. However, a real-world annual average would be closer to 0.05 euro/km ($0.07/mile) based on a mix of Stealth and Sport (gasoline) mode use. Actual economy and emission results will vary depending on individual driving habits and usage requirements.

Source (Fisker)

However, the new era of electric and partially electric cars is turning that convention on its head.

This was too brought to a head earlier this month when GM announced that Volt would get 230 MPG in typical city driving, and later that day Nissan tweeted that its LEAF would get 367 MPG.

In the case of the Volt, that number was arrived at by looking at the average amount of driving a cohort of city drivers did, presuming they were driving Volts and charging daily, and determined a total of 230 miles of driving would be covered over time for every one gallon of gas used.

Nissan’s number was based on a completely unrelated measure of the petroleum equivalence factor, which converts electric consumption into an equivalent amount of fossil fuel.

These numbers aren’t the end, but the beginning of a potential list of numbers that if displayed on window stickers may make it hard for consumers to compare and choose vehicles.  Some even argue that a dollars per mile measurement should be adopted, but due to volatility of energy prices and wide variability among different energy sources this method is insufficient as well.

Progressive Automotive X Prize is a marketing-neutral organization which will award $10 million to the winner of a competition among vehicles for the one that will get at least 100 MPG.

They are promoting the widespread adoption of a measure known as mile per gallon equivalents (MPGe), determined by the following formula:

MPGe = (miles driven) / [(total energy of all fuels consumed)/(energy of one gallon of gasoline)])

This system essentially levels the playing field for all energy sources propelling the car including electricity, gas, or alternative fuels.

As examples, using these methods, the Tesla Roadster consuming 53 kwh over 244 miles of driving would get an MPGe of 158. The Nissan LEAF traveling 100 miles on 24 kwh of charge would get 142 MPGe.

And what about the Volt?

Well the calculator found here would work for it too, but still missing is the value for the Volt’s MPG in charge-sustaining mode, Another problem is the fact that MPGe will vary as a function of range, from 170 MPGe for trips under 40 miles down to 58.2 MPGe on a 200 mile drive (assuming 50 MPG in generator mode.)

I asked John Shore who is Senior Advisor of Progressive Automotive X PRIZE what total driving distance he believes the Volt should be analyzed over.

He wrote:

Two relevant data points are the MPGe achieved at the 100 mile and 200 mile range requirements of the Alternative and Mainstream Classes, respectively. But it’s very important to note that the overall MPGe value used for scoring our competition will likely be considerably higher than these values, since MPGe over shorter ranges will contribute more to the overall value. Thus you might want to estimate the Volt’s MPGe at the various trip lengths listed in the table on page 36 of the Competition Guidelines – current version available here. You could then estimate a combined MPGe by taking a weighted average with the distribution weights shown in the table.

If we do the math he suggests up to 100 miles (99% of trips), the Volt then gets 167 MPGe, beating both the LEAF and the Roadster.

[NOTE: Graphic above is from Wall Street Journal article and illustrates yet another efficiency measurement, gallons per mile]

When the Volt concept was first unveiled in January 2007, GM said the car would get 50 MPG average when it was in generator mode based on computer simulations.

We understand the car will get up to 40 miles of pure electric driving from a fully charged battery, and that the average city driver will average 230 miles of cumulative driving on a gallon of gas, but what will the average fuel economy be in charge sustaining mode?

When the battery reaches a roughly 30% state-of-charge, its 1.4 L 4-cylinder engine will fire up, spin a generator, and produce electricity.

That electricity will purely be used to power the 110 kw electric motor, though the battery will still have that 30% hearty buffer and contribute to driving power demands as necessary. Furthermore, any braking, coasting or downhill opportunities will allow the recapture kinetic energy into the battery.

Clearly this series-hybrid design differs considerably then the typical power-split architecture of today’s modern hybrids like the Prius. It is of great interest to see how much fuel economy it can attain.

I recently asked Volt line engineer Tony Posawatz whether the production Volt would still get 50 MPG like the concept was promoted to. He said “that was just the concept,” though he didn’t specify what the real car will get.

Frank Weber when asked the same question said the story would eventually be told, but not right now.

So with this uncertainly why not a little speculation? What will the series hybrid mode fuel economy be? And how important is that number to us?
Note: There is a poll embedded within this post, please visit the site to participate in this post's poll.

Pure electric cars are generally rated in terms of kwh per 100 miles to show how efficient the vehilce is at using electrical energy. Since the Volt will drive the first 40 miles without gas it is appropriate to apply that metric to those miles.

Per GM’s press release, “applying EPA’s methodology, GM expects the Volt to consume as little as 25 kilowatt hours per 100 miles in city driving.” GM noted that this methodology is new and still under development in draft form.

Since we know the Volt will be able to use a maximum of 8 kwh of energy storage, then it could be concluded the Volt’s all electric range (AER) should come out only to 32 miles in city driving [100 mi/25 kwh x 8 kwh = 32 mi]. This is lower than the omnipresent 40 miles GM has stated since the beginning.

I sought clarification from Volt executive Frank Weber.

“The Volt is achieving 40 miles in the city and highway cycle, ” he said. “Nothing has changed.”

He noted however that in the new testing methodology “EPA is assuming a daily charge and is applying some real world factors that will degrade the EV range.”

“EPA has considered varying temperature and drive style conditions in their methodology,” explains Weber defining what he means by real world factors, and distinguishing how the new test differs from the old one.

“The cycle tests are run at a single temp and would not reflect range variation due to accessory loads,” said Weber referring to the older methodology from which the 40 mile designation was originally estimated.

I contacted Andrew Simpson, who is a Senior Research Fellow in plug-in vehicle technology at Curtin University, Australia, and previously worked at Tesla Motors and completed the EPA range certification testing of the Tesla Roadster. He said the older method is called “the SAE Recommended Practice J1634 “Electric Vehicle Energy Consumption and Range Test Procedure”. However, he notes “the standard is a bit outdated and SAE have formed a committee to revise it.” It is this committee that has written the draft.

“The revised 1634 procedure is an abbreviated version of the previous and consists of a battery capacity/characterization test followed by an finite number of drive cycles to measure energy consumption and estimate range,” said Vineet Mehta also of Tesla Motors.

The original J1634 procedure was written in 1993 and technically discontinued in 2003. The revised SAE J1634 draft is expected to be completed by December 2009.

So will the Volt still get 40 miles under real world standard conditions in the city? And what will the number be on the highway? These facts as well as the Volt’s MPG in generator node remain undisclosed.

It is important realize that EV ranges will vary considerably from what the manufacturer claims just as MPG does, and depend considerably on driving aggressiveness and use of accessory loads.

The sticker shown above was for the original EV-1 showing how the car got 30 kwh/100 miles in the city and a 20% more efficient 25 kwh/100 miles on the highway.

Why was this? Of course because GM announced that the Volt would get an EPA rating of more than 230 MPG. As exciting and compelling as that number is, it has raised as many questions as answers.

GM has not enunciated in exact detail how that number was arrived at.

But, while at the GM event I had the chance to get the answer from Larry Nitz, GM’s executive director of hybrid powertrain engineering

Can you explain how GM and the EPA arrived at the 230 MPG city estimate for the Volt?

In a conventional car there is two things that cause your efficiency to vary. The speed and intensity of your driving, and the environment; do you need HVAC, lights, etc.

With the Volt, you add two more things that makes your mileage vary, how far you drive, and how many times you plug in during the day.

So on any given day if you have plugged in your EV, range at low intensity driving, like the EPA city cycle is, is 40 miles. If you drive more aggressively your EV distance will be reduced.

Now, after you’ve depleted the battery, in the case of the Volt, the engine will start and the engine will keep the vehicle running for as long as you have fuel in the tank, and the fuel economy you have there matters too.

So in the calculation of the label, for that 230 you take into account the EV distance, the fuel economy after you depleted the charge, and the EPA used a traffic survey that was done in 2001 to create a composite.

They looked an an aggregate sample of the population and how far they drove in a day.

With the data we have and the data we shared with the EPA, from that value, they’ve created what’s called a utility factor.

It was a snapshot in time and based on this dataset we will weight the value on an aggregated probabilistic way what the value of the EV distance is, and we’ll also weight one minus that for the charge sustaining distance.

You go through this calculation that accounts for the fuel use and you come out with a number and the number is 230.

That’s a big number and you ask, will I ever get that number?, and its kind of interesting. In a normal car if you drive it high intensity you can never get the EPA , but in the Volt you always could, it just depends how far you have to drive. If you drive under the EV distance its infinite.

What was the percentage of time or miles in EV mode that was used?

The number was calculated by the EPA using this probabilistic curve and it had the statistics of the population in it.

How about the petroleum equivalence factor (PEF), is that included?
There will be on the label itself an accounting for the gasoline equivalent of KWH used. That’s a separate conversion that will get melded in another way and is not included in the MPG estimate.

So in summary, Nitz explains that the average Volt driver charging his car nightly can expect to burn one gallon of gas for every 230 miles traveled over time based on the behavior of a particular random population that was studied in 2001.

The highway calculation will be lower but the composite average is expected to be greater than 100 MPG.

The EPA has not confirmed this number yet because they haven’t tested the car, but they agreed to the testing method and GM is confident these are the numbers that will eventually become official.