It seems that two of the unlikeliest brands, Lincoln and Buick, are among the most progressive thinkers in the entry-level American luxury car market: both now offer no-cost hybrid versions of their cars. The Lincoln MKZ is a full hybrid, but Buick has gone a slightly less aggressive route -- though no less intelligent -- with its LaCrosse eAssist.
For the 2012 model year, buyers of the full-size LaCrosse can choose between two powertrains at the same base price: a newly fortified, 303-hp 3.6-liter V-6, or a 2.4-liter four-cylinder with a mild hybrid system strapped on.
“Mild hybrids,” as we call them, can’t propel the vehicle under electric power alone. They perform the same main function as other hybrids, which is that they recapture kinetic energy that would have otherwise been lost to heat in the braking system, store it in a battery, and then use it to propel the car at a later time. The LaCrosse’s hybrid system, along with some other intelligent tweaks to aerodynamics and rolling resistance, posts an enormous gain in EPA ratings: last year’s four-cylinder scored 19/30 mpg; the eAssist version bumps those numbers to 25/36. That’s subcompact fuel economy in a full-size car. (We averaged an indicated 29 mpg over a 120-mile mostly back-road route with three passengers and air conditioning.) Best of all, the hybrid system’s additional torque helps this new LaCrosse get to 60 mph 0.2 seconds sooner than the last car, according to Buick.
The performance increase is possible because the LaCrosse’s simple hybrid system doesn’t add a lot of weight. Total curb weight is within 6 lb of the non-hybrid car -- to offset the extra weight of the 0.5-kWh battery, wiring, and motor/generator, the eAssist LaCrosse uses aluminum in a few key areas -- wheel hubs and hood, to name two -- that were previously steel.
The battery is mounted behind the rear seats, and trunk space suffers a bit: its capacity drops from an already smallish 13.3 cubic feet to 10.9. But the LaCrosse has an enormous back seat -- a worthwhile tradeoff if you carry more passengers than cargo.
To assist in the miserly mission, the 6-speed automatic has been revised for reduced friction. Called the Gen II Hydra-Matic 6T40, the new transmission performs shifts more quickly and will appear in other GM products in the future. The final drive ratio has been significantly lengthened, from 3.23:1 to 2.64:1, and as a result, first gear is loooong: at the 7000-rpm fuel cut, the LaCrosse is doing 43 mph. It also means the engine is asleep in top gear on the highway. Thankfully, shift quality is excellent, since two-gear downshifts are occasionally necessary to maintain cruising speed on hilly interstates.