GM's next-generation Duramax diesel is coming--and it boasts a host of new technology tweaks to help it deliver better gas mileage.

The Duramax name is about the only thing that GM's new ultra-efficient diesel engine, in final phases of development, shares with the current iteration. The diesel currently sold under the hoods of Chevy Silverado and GMC Sierra trucks (the hybrid version's shown above) is a 6.6-liter torque monster co-developed with Isuzu back at the turn of the millennium. Expected the new Duramax to produce in excess of 310 horsepower and 520 pound-feet of torque, coming mighty close to the prodigious output of the current version (365 hp, 660 pound-feet) despite a displacement smaller by 2.1 liters. Of note, GM engineers developed this new Duramax entirely in house, throwing out all assumptions and preconceived notions about diesel engine design.

GM says it will use this new diesel in its Silverado and Sierra half-ton pickups built after 2009, as well as the HUMMER H2 should that brand still be in the corporate fold upon the engine's release (doubtful: "Last HUMMER Dealer in Vegas Shuttered"). Very clever packaging allows the entire unit, turbo/intercooler and all, to fit in the same space as a GM small-block V-8, an engine known for its tidy packaging.  This should make it applicable not only to trucks but to other rear-wheel-drive vehicles in the General's stable (diesel Camaro, anyone?).

Remarkably, the engine does not have traditional intake manifolds, and the exhaust manifolds spill into the 72-degree V-bank between the cylinder heads where a variable-vane turbo is also conveniently located for quick spooling and minimal heat loss. The pressurized intake charge is fed right through the valve covers via trick ports that we can't wait to see illustrated in detail. In another change from the current Duramax that uses pushrods for valve actuation, the new engine's four valves per cylinder will be activated by dual overhead camshafts.

It all adds up to fuel efficiency gains of 25 percent, a CO2 emissions reduction of 13 percent, and particulate and NOx reductions of over 90 percent when compared to GM's current diesel trucks. The engine will be built at GM's Tonawanda, N.Y., assembly plant.

Cummins is readying a new smaller diesel for the Dodge Ram pickup, as is Ford for the F-150 and other pickups. Will all of this diesel development trickle down into American diesel passenger cars, or will diesel remain predominantly a truck engine in the minds of the American driver?--Colin Mathews

The Insurance Institute for Highway Safety (IIHS)--the industry-funded group that mashes cars into walls so that you don't have to--says GM's big crossover vehicles are so good at protecting passengers, they're giving them the Top Safety Pick designation.

The TSP award goes to cars and trucks that earn "good" crash ratings for front, side, and rear impacts, and also have standard stability control.

The GM crossovers included in this set are the 2008 GMC Acadia (the hapless victim actually tested by the IIHS), and its bunkmates--the 2008 Saturn Outlook and 2008 Buick Enclave. The agency says the 2009 Chevrolet Traverse also will get the designation, since it's structurally similar to the other vehicles.

The IIHS says the rating applies to crossovers built after March 2008.

GM says a new XFE version of its big pickups and SUVs adds 1 mpg to their fuel economy ratings, by adopting some aerodynamic and tire tweaks.

The changes to the Silverado/Tahoe and Sierra/Yukon lineups improve fuel economy by 5 percent on the highway and 7 percent in the city, and improve the trucks' coefficient of drag. The fuel economy ratings improve from 14/20 mpg to 15/21 mpg.

All the new XFE models are rear-drive trucks outfitted with GM's 5.3-liter V-8 and six-speed automatic. It's a flex-fuel-capable engine that puts out 320 horsepower in the SUVs and 315 horsepower in the trucks. A new ratio on the rear axle, lightweight wheels, and an aluminum cylinder block and heads help in the fuel-economy push, as does a tonneau cover for the truck bed, a deeper air dam, a slightly lowered suspension, and some more aluminum parts to reduce weight. Low rolling-resistance tires complete the package.

Despite the changes, the SUVs keep their 6,600-pound tow rating, while the trucks' towing rises to 7,000 pounds.

The Insurance Institute for Highway Safety (IIHS) has tested the crashworthiness of compact trucks in side impacts--and the Toyota Tacoma is the only truck to emerge with its safety reputation intact.

The Tacoma earned the IIHS's "good" rating for side-impact protection in the test of 2008 models. Its optional side and curtain airbags provided enough protection for crash dummies to get the rating, the agency's highest. The Tacoma also has a "good" rating for front-impact protection.

Other compact trucks didn't fare as well. The Dodge Dakota, Ford Ranger, and Nissan Frontier all were rated "marginal" by the insurance industry-funded group, while the Chevrolet Colorado (and we correlate, the nearly identical GMC Canyon) was given a "poor" rating for side impacts.

The IIHS notes that all the vehicles involved in the test save for the Frontier and the Tacoma lacked stability control. (The GM trucks will have it standard in 2009.) The Tacoma was the only truck offered with side airbags as well. It also notes small trucks have the highest driver death rates on the road.

As a result of these latest tests, some of TheCarConnection.com's safety ratings for reviewed vehicles have changed. Click the trucks above if you're shopping and want to find more about the safety ratings of the vehicle of your choice.

This morning's announcements from GM were met with a big public-relations offensive which included a special bloggers-only conference call with vice chairman Bob Lutz. TheCarConnection.com and Gaywheels.com were invited to be on this very limited call, the highlights of which appear below in brief notes:

• Lutz says GM is fundamentally altering its product portfolio in the U.S. and it will resemble more closely those in Europe and Asia--with much more fuel-efficient vehicles.


• In regards to struggling Saturn, "Our worry with Saturn is that the franchise is not generating enough volume," Lutz said. "We had planned to short-cycle the Aura" and replace it with the mid-size Opel Insignia, he said. By holding on to the current Aura for a few more years, GM can conserve cash.


• Conversely, he says the Buick Invicta is one of "nicest things we've ever done." The car may not carry that name in production.


• "I hope fuel doesn't get more expensive," but Lutz says the introductions of vehicles like the new Cadillac SRX and Chevrolet Equinox will draw its lineup slightly down in size and dramatically higher in fuel economy.


• The new Chevrolet Cruze is expected to have 40+ mpg fuel economy in a package that's larger than today's Cobalt, Lutz says.


• He hints that GMC will get a crossover, substantially smaller than the Acadia, equipped with four-cylinder engines. GMC is expected to get a version of the new Chevrolet Equinox; it's "so different" you would never guess they were similar under the skin. (The GMC version is expected to be called the Terrain.)


• "As U.S. fuel costs approach fuel costs of the rest of the world...the vehicle park of the U.S. will come to resemble the vehicle park of the rest of the world."


• As for Pontiac, it's a vital part of the Buick-Pontiac-GMC group, he explains. Buick will be positioned at the premium end, with GMC selling trucks and crossovers. Pontiac will be low-end passenger cars. Offer "excitingly styled, fun to drive cars that are affordable," and largely based on Chevrolets.