A recent article on the cover of the industry trade journal Automotive News reported that GM has canceled plans to develop a replacement to Cadillac's Northstar V8. Instead, GM's direct-injection 3.6-liter V6 (with maybe even a turbodiesel six available) would become the Big Kahuna in the sedan line-up. This is partly blamed on the new CAFE fuel economy regulations. But there is a bit more to the story than that.

Sure, there is a certain prestige in having a DOHC V8 in a luxury sedan. It earns bragging rights in enthusiast magazines and Internet forums, where everybody envisions themselves as a "high roller." Given that Cadillac used to bill itself as "The Standard of the World," could a V8-less (save for V-series models that use a version of the Corvette's pushrod V8) Cadillac regain that status?

Thing is, that argument seems to have been answered already in the marketplace. Buyers in this vehicle class—Acura RL, BMW 5 Series, Cadillac STS, Lexus GS, Infiniti M, and Mercedes-Benz E-Class—overwhelmingly choose six-cylinder engine versions. (Of course, they have no choice for the RL.)

This decision is strongly helped by fantastic six-cylinder engine options, which combine big power and decent fuel economy. We bought a 2008 Cadillac STS, with its new standard 302-hp direct-injection V6 engine, to put through our track tests. It sounds great and gets to 60 mph in 6.4 seconds. It even returns 18 mpg overall on regular fuel. We never tested a STS with the Northstar V8, but it's really hard to want more than that this V6—or to justify the V8's extra 18 hp, 43 lb-ft of torque, heavier weight (GM says 150-200 pounds) and close to $6,000 price premium.

It's not just Cadillac. The BMW 535i we tested uses a 300-hp, twin-turbocharged, inline-six that gives effortless acceleration (0-60 mph in 5.8 seconds) and an impressive 22 mpg on premium. The six-cylinder Lexus GS350 actually has more horsepower (303 vs. 290 hp) than last year's 4.3-liter V8 GS430. (That changed for 2008 with the top-level GS getting the Lexus LS460's 4.6-liter, 342-hp V8.) But these six-cylinders are all refined and responsive, so you're not exactly suffering.

With this level of performance and refinement, more companies are following suit in moving away from V8 power; Ford announced several months ago that the top engine in the Lincoln MKS luxury sedan would be a turbocharged, direct-injection six-cylinder.

Arguing issues of need vs. want are tricky in the automotive world, especially when it comes to luxury sedans. After all, you can argue that no one needs one of these cars, anyway. But it strikes me that the aforementioned V8 models don't make much sense anymore, except for bragging rights at the country club. And if that's what important to you, use the money you saved on the six-cylinder's lower purchase price and cheaper running costs and go buy the V8's model badge to glue on the car's deck lid.

—Tom Mutchler