CHANTILLY, VA – General Motors Co. pares its Buick LaCrosse engine offerings by one, announcing today it will discontinue availability of the 3.0L V-6.

The base engine remains the 2.4L Ecotec I-4, while the lone optional powerplant is the 3.6L V-6.

GM’s motivation: simplification. Buick’s all-new midsize Regal, due later this year, has no 6-cyl. engine option, featuring the 2.4L Ecotec and an optional 2.0L turbocharged I-4.

In addition, the I-4’s capabilities are well within a LaCrosse buyer’s expectations, GM tells Ward’s here at a preview of the ’10 fullsize sedan.

“As Buick continues its transformation, new products like the 2.4L-powered LaCrosse CX are helping us reach all-new customers,” Buick Product Marketing Director Craig Bierley says in a statement. Particularly those customers who are sensitive to rising gasoline prices, he adds.

The Environmental Protection Agency rates an Ecotec-equipped LaCrosse at 19-30 mpg (12.4-7.8 L/100 km) city/highway.

The 182-hp I-4 delivers peak torque of 172 lb.-ft. (233 Nm) at 4,900 rpm and was named one of Ward’s 10 Best Engines for 2010. The 3.0L V-6 has a 255-hp rating and generates peak torque of 217 lb.-ft. (294 Nm) at 5,100 rpm, compared with the 280-hp 3.6L V-6’s 259 lb.-ft. (351 Nm) at 4,800 hp.

All three engines feature direct injection.

The V-6s, in front-wheel-drive configurations of the LaCrosse, are both rated 17-24 mpg (13.8-9.9 L/100 km) city/highway.

All-wheel-drive, previously available only on LaCrossses equipped with the 3.0L V-6, now becomes available on cars featuring the 3.6L engine, GM announces today.

Meanwhile, GM remains high on the 3.0L V-6. “Especially in China where there is a displacement tax,” says Jim Federico, global vehicle line executive-midisze cars.

The 3.0L V-6 is the base engine in the Cadillac CTS car line and SRX cross/utility vehicle. It also is available in the Chevrolet Equinox and GMC Terrain.

“You never know – we could see a displacement tax here someday,” Federico tells Ward’s here at a Buick LaCrosse preview.

The state of Washington last year considered taxing vehicles based on engine size, from $70 for a 2.0L engine to $600 for engines 8.0L and larger. The plan eventually was scuttled.

The base LaCrosse starts at $26,995.

– with Eric Mayne