A mystery has been solved.
What mystery? How the 2016 Chevy Malibu Hybrid gets an estimated 5 mpg better fuel economy than the 2016 Volt when running in gas-burning hybrid mode even though both use the same essential “drive unit,” or gas-electric transaxle.
The 1.5-liter compact-class Volt is a 53-mile extended-range EV, but in gas operation after the battery is depleted, it essentially morphs back to a 42 mpg hybrid. The 1.8-liter midsized Malibu is a full time hybrid with preliminary mpg estimated at 47 mpg, has more power and is physically larger as well.
To observant readers, something did not check this spring when the hybrid Malibu was introduced. The Volt had been revealed with fanfare in January, and General Motors made quite the to-do about the Malibu being co-developed with the Volt to set a new benchmark in efficiency.
But, some reasoned, if the Volt was the new “halo” eco car for General Motors, how was it being trumped by the Malibu in any of its operation modes? Its EV range is class leading, but why should its mpg be less than a bigger sibling using its own powertrain? As it is, this is the case.
At the time, people speculated why this could be. Chevrolet did not provide the answer to us upon request, and that was a recipe to stir the pot more.
After all, think about it. The 1.8-liter engine in the Malibu could burn more fuel than a 1.5 liter in a Volt. A larger car as the Malibu is presents a broader frontal profile so that could add to mpg-sapping wind drag. Higher system power derived more from the gas engine in the Malibu over the Volt led common sense to conjecture if anything, the Volt should get better mpg. The Malibu has slightly wider tires too.
Some people took to guessing. Perhaps, some offered, because the Volt has a big 18.4-kilowatt-hour battery it’s much heavier than the Malibu with its small 1.5 kwh pack.
Nope. The cars are within 86 pounds of each other. The Malibu is 3,457 pounds, the Volt 3,543, and the weight of one half-grown kid is not enough to cause a 5 mpg disparity.
So What is the Answer?
It’s all attributable to differences in the two cars’ powertrain, and trade-offs were made.
In short, the Volt is optimized to operate as an EV with gas backup, and the Malibu Hybrid is simply a regular full hybrid.
Since the Malibu Hybrid always uses gas, like a Toyota Prius or other hybrid would, it was optimized for maximum fuel efficiency.
It also when launched will enter the hotly contested mid-sized hybrid sedan space presently dominated by the 40/41 mpg Toyota Camry Hybrid, 42 mpg Ford Fusion Hybrid, 41/42 mpg Hyundai Sonata Hybrid, and best of all – 47 mpg Honda Accord Hybrid.
A Volt-like 42 mpg would have made the Malibu Hybrid just average when General Motors is coming from behind into a market in which its eAssist mild hybrid had been its only offering.
The Volt on the other hand is meant to avoid using gas altogether. It already was in a class by itself above blended plug-in hybrids with 38 miles EV range. Its new 53 miles is now nearly double the next-nearest 27-mile EV range Hyundai Sonata PHEV, so that is its primary competitive advantage.
A weak point had been the Volt’s 37 mpg in premium-gas operation, and the 2016 now runs on regular returning 5 mph better economy, so that is a plus.
Engineers had also been tasked to cut costs from the Volt and Malibu and this they have. Last week during its Global Business Conference, the company said it has increased Volt profit potential by $3,500 per unit.
In reality, automakers have to pick their priorities on what they can profitably deliver at a price point.
Other items not on the Volt include an independent rear suspension that the Cruze gets, and unavailable is a 6.6-kilowatt onboard charger, even as an option, and despite owner requests. The Volt is altogether improved, but a few things had to give.
With that as background, the Malibu Hybrid is different in three fundamental ways, according to Greg Hubbard, chief engineer, Electric and Hybrid Propulsion Systems. These roughly add up to the missing 5 mpg estimated as follows.
2 MPG – EGHR
The Malibu Hybrid is the first Chevrolet to utilize Exhaust Gas Heat Recovery (EGHR) but the Volt does not have it.
This innovation uses heat that would otherwise go to waste to warm the cabin interior as needed and the engine.
This engine heating lets the car warm to peak efficiency faster. In a hybrid that does not have the Volt’s luxury of running very far with gas engine off, this is a priority.
The Volt on the other hand caters to people who want to stay off gas. Its engine might have gotten EGHR, and all the thought behind the decision was not explained, but it would have added more cost to a car in which hybrid mode is a secondary operation.
At least the argument can be made to that effect. The top-mpg hybrid, the Prius, may get 55 mpg or better, so the 13 mpg disparity has remained the same from 2015 to 2016 between the two loosely compared rivals. Where mpg in gas operation matters for the Volt is when people want to travel farther than EV range.
High-mileage drivers have to weigh this when considering a Volt. If the Volt got up to 50 mpg, it would have been less of a head-scratching moment, but this is what we have. EGHR would not in itself have added to that much, but it is part of the formula of why the bigger Malibu nets better gas mileage.
2 MPG – Permanent Magnet Motor
The Malibu utilizes two permanent magnet motors, both utilizing rare earth materials. The Volt utilizes a ferrite magnet design in its smaller of two electric motors.
Sometimes people get confused about rare earth permanent magnet motors versus GM’s ferrite motor and they think the ferrite motor is an induction motor. Actually, the ferrite motor is still a permanent magnet motor. Its permanent magnets are just made from ferrite (iron) instead of from a fancier mix of magnetic metals that include rare earth metals.
The Volt’s design is actually a benefit in that it cuts cost, does away with rare earth materials often sourced from China and with potential supply and cost instability. It does save on production costs in the Volt but is fine for EV mode, less ideal in hybrid mode.
On the other hand, the Malibu Hybrid’s motors have better suited torque and electrical efficiency characteristics for hybrid operation.
1 MPG – Performance Tuning
The Malibu upon acceleration leads with power from its gas engine, but the Volt leads with its electric motors.
This gives the Volt a more fluid, instant torque EV feel even in hybrid mode and is easier for the Volt to do with power in reserve in its large li-ion battery – even when it is “depleted” it has usable energy.
The Volt favors immediate use of the battery to provide fast reaction to driver demand and then the gas engine follows along later.
The Malibu Hybrid however has a smaller battery, so makes more immediate use of its gas engine during acceleration.
This avoids conversion losses the Volt experiences from using the battery and then recharging it from the gas engine in the Volt.
Two Different Solutions
If GM had told bean counters to take a hike, might it have pulled off 50 mpg for the Volt?
That’s not known, but more certain is human psychology tends to desire more of everything. Realities however more often dictate a different outcome.
The Volt as mentioned, is meant to run as an EV with gas backup in charge-sustaining mode. It does things the Malibu cannot like avoid gas for months on end.
The Malibu Hybrid is to be competitive in its market segment.
One might speculate still more could have been done, but GM has engineered both vehicles to the best they can be within constraints.
Improvements are ongoing, and not out of the question is whether the Volt in a couple years might see a bump in its battery capacity, as was the case in 2013 and 2015. A 0.5 and 0.6 kwh increase came in two year intervals after the 2011 introduction and Volt gen-one had a 16.0, 16.5 and 17.1 kwh pack during its life.
What else might we see? No doubt customers will keep providing feedback which was used to redesign the gen-two Volt.
After speaking with executives and engineers, it is plain GM knows what its customers have asked for and will keep working to improve its products.