2012 Buick LaCrosse with eAssist: First Drive

The 2012 Buick LaCrosse will be the first model to receive GM's eAssist mild-hybrid system, a new take on a design used in past cars like the Chevrolet Malibu Hybrid and Green Line versions of the Saturn Aura and Vue. Regrettably, those cars delivered maximum public-relations pain for their mileage gain: They failed to provide the efficiency of the day's full hybrids, and critics thought GM was disingenuous to use the hybrid term. The newly named eAssist boasts up to 25% better mileage than the current four-cylinder LaCrosse, and it drives well, too.

GM's estimated mileage for the eAssist LaCrosse is 25/37 mpg city/highway, compared with the 2011 LaCrosse four-cylinder's 19/30 mpg. For the 2012 model year, the eAssist version will become the car's standard drivetrain, supplanting the gas-only four-cylinder. Buick says the car will cost roughly $30,000, almost $3,000 more than the 2011's starting price. Along with the drivetrain comes low-rolling-resistance tires, underbody aerodynamic treatments and automated grille shutters that close at higher speeds to improve aerodynamics.

Technically, eAssist is a gas-electric hybrid design, similar in principle to Honda's Integrated Motor Assist, but it doesn't go as far. Rather than a large motor on the crankshaft, eAssist simply replaces the 2.4-liter four-cylinder gas engine's alternator with a single motor/generator that's more robust than a typical alternator but not as powerful as a traditional hybrid's drive motor. As in the previous iteration, it connects to the crankshaft like a regular alternator, via a belt, which gave the system its engineering name: belt alternator starter, or BAS.

The conventional starter motor is retained, but the motor/generator is responsible for restarting the engine more seamlessly after it turns off, which it does whenever the car comes to a complete stop. The motor/generator also provides 15 horsepower of assist when accelerating and 15 kilowatts of regeneration when coasting and braking. Putting energy back into the lithium-ion battery pack for reuse is one of the fundamentals of hybrid efficiency. The previous BAS provided less than 3 hp and 5 kilowatts of regeneration and used a lower-voltage nickel-metal-hydride battery. The new pack more than doubles the power to 115 volts.

The LaCrosse with eAssist I drove accelerated confidently and smoothly, and, more important, it braked smoothly, too. The brakes didn't feel like the regenerative braking in normal hybrids; they were more natural, and the linearity was good. Frankly, we're leery of the light-electrification movement partly because it compromises the braking feel in some of BMW's "Efficient Dynamics" cars. In that system, the alternator is on a clutch that brings it in and out of the equation. Because the eAssist component is also a motor, Buick says, it's actually used to smooth the six-speed automatic transmission's shifts.

It also allows the fuel injectors to shut off all the way down to a stop, whereas normal cars typically feed fuel when decelerating in lower gears, Buick says. Further efficiencies come from a final drive ratio of 2.64 rather than 3.23 in the gas-only version, enabled by the electric motor's added torque.

The only shortcoming I noticed was what the battery pack does to the trunk space: The volume is cut down to 10.9 cubic feet from 13.3 cubic feet, which isn't terrible, but the main disappointment is that the pass-through is relatively small when the backseat is folded. The gas-only 2011 car has full folding rear seats, and even the first-generation BAS sedans like the Malibu Hybrid had a trunk-wide opening to the cabin, even though the battery pack compromised the height.

The eAssist drivetrain will also appear in the Buick Regal and, certainly, more GM brands. Compared with a full hybrid, this approach is relatively inexpensive to manufacture. At 0.5 kilowatt-hours, the battery pack probably costs a few hundred dollars rather than thousands, and the price should drop over time. I wouldn't be surprised if eAssist and similar designs become standard equipment across the market someday as automakers chase higher mileage.


Chris Morgan

The specification of this car is awesome its a really good effort done by the company


The 2012 adds more standard kit which is part of the price increase. 17" wheels and foglights weren't standard on 2011 cx models. There is likely more equip that was added as well.


A $3,000 price increase is ridiculous. I'm sure Avis is pissed.


I'm not fully clear on something: Does the BAS take charge of starting the motor in hybrid function, or does it give assist to the starter motor?


@ Lloyd,

a civic hybrid cost $5k more than a civic HF, so $3k isn't all that bad. i'm sure avis isn't too pissed about it.

Mark L

Good looking car



Buick is adding content that should've been standard on the 2011 model so you aren't just paying for the eassist system. The hybrid system is probably half that cost. Buick is moving the lacrosse base price away from the regal for less overlap.


The LaCrosse must now have the highest base price in it's segment and that's only going to drive away the senior citizens that still buy the brand.


A 22+% change in gearing is crazy.
Just how slow will acceleration be if the battery is drained?


Regardless of who is buying lacrosse it outsells tl, avalon and es350 every month. Buick is attracting younger buyers and lacrosse is outselling the car buick targeted. Mission accomplished. The car is also getting a 300hp v6 for 2012 just like impala.


@ george,

the battery will never become drained. it will function the same way a prius does (or any other hybrid on the market today), performing a balancing act between recharging the battery and using battery power to provide additional power when needed. anyone who's driven a hybrid for a while (i own a prius), is familiar with this process, which is pretty transparent.

Cody is generally correct. It's possible that you could climb a very steep, long hill and run the battery pretty low, but it's unlikely, and remember that the engine is no slouch. >180 hp and six speeds should cover it, regardless of the final drive.

As for the starter motor, it is a conventional separate component that meshes with the flywheel. Runs off a regular 12-volt battery, which I believe all hybrids and electrics retain, at least for accessory purposes. I suspect the regular starter is used when the car is cold, but when I took my turn in a warm LaCrosse, it seemed to use the motor/generator when I turned the key.

Gary Fox

I fly over 90 segments a year and have literally seen several thousand Buick Lacrosse as rentals. The Regal, Lacrosse, and Enclave have become the new Malibu, Impala, and Caravan of the rental car world.
Recently an Enterprise rental fleet director in Atlanta told me Buick is struggling to sell or lease enough Regals to break even so the rental car companies are getting some great deals. He said Americans complain the car is to small and underpowered.


Looking forward to the calculation of how many years it will take to pay off the $3,000 eAssist premium in saved gas (factoring in the extra standard equipment of course).


this is a nice car in its own right, and this improves both the performance and fuel economy of the 4-cyl version. i doubt anyone considering this car will bother to calculate how long it would take to make up the $3k..especially considering the competitors in this price point.

Brian Greenberg

The car cost $3,000 more and you get no spare tire (tire inflation kit only) and a smaller gas tank!? Given GM's track record with faulty EPA readings (ie my wife's Equinox) I'll pass.



Gas tank is smaller due to increased mileage, you should have plenty of range with a 15+ gallon tank.


I don't buy what you're saying for a minute. In fact truecar.com has given buick good ratings in recent months for balancing incentives, transaction prices and inventory. Most of gms fleet sales are from chevy. Buick isn't even a high volume brand so its not a mainstay of rental agencies. Malibu and impala are gms main fleet cars.

WoW! can't wait!!!! this could be the final big push Buick needs to continue changing there demographic!


The electric assist is primarily at low speed. 15hp@1000-2200. GM doesn't say how quickly it tapers off.
Imagine setting the cruise control at 65mph, and encountering a hill (and you have the AC on, and a full load of adults)
65mph in 6th gear is just under 1700rpm. The engine can make roughly 43hp, and 68hp with electric assist.
If the battery becomes drained (it doesn't have to be fully), the transmission will downshift to 5th gear, the engine speed will now be 2250, and the engine alone can make roughly 64hp, 79 with assist.
If that is not enough to maintain the set speed, the transmission can downshift into 4th; engine speed will be just under 3300 and can develop roughly 96hp, (and maybe 105 with assist; assuming it operates above 3000rpm)
If that is still not enough, 3rd gear is available and 130+hp is possible at just over 4300rpm.

That >180 hp is available in 3rd gear at >100mph.
Maybe/hopefully GM will use the stroker 2.5 engine for greater mid-range power.

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