Lab Of LuxuryLab Of Luxury

General Motors has turned back the clock with the release of a trio of new SUVs for 2002--the Chevrolet TrailBlazer, the GMC Envoy, and the Oldsmobile Bravada--that feature a new breed of inline six-cylinder engine.

Just when it seemed the auto world had completely converted to the popular V-6 engine, GM has introduced its straight six, a form considered by most everyone except BMW to be an auto anachronism--the equivalent of the buggy whip. But GM's new SUVs and state-of-the-art engine already are winning major industry awards.

In the '60s, the V formation--side-by-side rows of three cylinders connected at an angle--began to take hold, driven largely by GM.

V-6 had some advantages in packaging, but there are physical principles that benefit the inline design, mainly avoiding vibration, a killer in the auto context.

The inline is more balanced and develops less internal vibration than the V-6. Excessive vibration presents many problems in terms of engine efficiency and longevity--plus people don't want to drive vehicles that buzz. Clever engineers can quell the vibration of the V-6 using devices such as counterrotating balance shafts but at added complexity and cost.

The new motor delivers the performance of an eight-cylinder engine with the gas mileage of a six. Power is a very respectable 270 horsepower and tops the V-8 in the rival Ford Explorer.

A week driving the Bravada proved the new engine to be the smoothest six-cylinder truck engine yet.

Cordell Koland is an auto writer in Silicon Valley.