The G8 is a rear-wheel-drive sedan, Pontiac's first full-size car since the Bonneville was discontinued in 2005.It becomes the Pontiac flagship, being bigger than the mid-size front-wheel-drive G6, and it takes that spot at the top of the line with pride, being a very good car, with no weaknesses.At least not with the V8-engined GT, which Pontiac accurately bills as the most powerful car on the market for under $30,000.But it's not just powerful; there's a wonderful six-speed manual automatic transmission, the ride is comfortable without being soft, and the handling is taut.It all works.

And it looks good: smooth and muscular, with an unmistakably Pontiac nose.The interior is comfortable and tidy, with good instrumentation and a reasonably roomy rear seat.The standard cloth seats are excellent, with good bolstering and lumbar support.Leather is optional.The GT features an 11-speaker Blaupunkt sound system.

Even with 361 horsepower, the G8 GT gets 15 city and 24 highway miles per gallon, on regular fuel.Premium is recommended but not required.When Pontiac measures the horsepower on the dynamometer, guaranteed, they use premium fuel.

It comes with a comprehensive list of safety features, including electronic stability control, curtain airbags, and Onstar.

The V6 G8 uses the same engine that's in the Cadillac CTS.It doesn't rate the same praise as the GT because it doesn't have the V8's power, six-speed transmission or taut suspension or steering.It costs $2400 less, and its highway mileage is only one more mile per gallon, at 17 city and 25 highway.

The GT is the hot setup.The 6.0-liter, 361-horsepower V8 engine, using a six-speed manual automatic transmission, totally changes the car.Starting with the hood scoops, passing through the seat of your pants with the tuned suspension, and ending at the four polished stainless exhaust tips.Inside, it adds dual-zone air conditioning, a leather wrap steering wheel with controls, color LCD display, and six-disc CD with Blaupunkt 11-speaker sound system.

The V6 engine in the G8 makes 256 horsepower and uses a five-speed automatic with driver shift control.Standard equipment includes air conditioning, cruise control, four-way power front seats, tilt/telescopic steering wheel, lighted visor mirrors, compass in rearview mirror, power windows and locks, AM/FM/CD seven-speaker sound system with auxilary input jack, 18-inch aluminum wheels, fog lights, and tinted glass.

Options include a Comfort and Sound Package ($795), an upgrade to dual-zone A/C and 6CD with MP3 and premium speakers.

The GT adds dual-zone air conditioning, a leather wrapped steering wheel with controls, color LCD, and 6CD with Blaupunkt 11-speaker sound system.That's in addition to the 6.0-liter V8, six-speed transmission, tuned suspension, and special trim.The Premium Package ($1250) includes leather upholstery and heated, six-way power front seats.

Safety equipment includes anti-lock brakes, stability control, traction control, remote vehicle start, driver info center with tire pressure monitor, battery run-down protection; front, side and curtain airbags, and one year of Onstar Safe and Sound, which does not include navigation guidance.

In the fenders behind the front wheels, there's another opening.On the left side is an air intake, while the right side is merely there to match the left.

The roofline is sweeping enough to disguise the fact that there are four doors, and the hips lift but aren't as high as they might be, and the spoiler is tidy.The G8 GT uses clear taillight lenses, and has four polished exhaust tips, the G8 red with two.

One wonders why GM doesn't try harder to design better looking wheels.The G8's twin five-spoke 18-inchers (painted aluminum) look better than the G8 GT's five-spokes (brushed aluminum), and the optional 19-inch wheels aren't that much better.A killer set of wheels will cause the G8 to turn heads, which might not happen without help.

The seats are comfortable, adjustable four ways in the G8 and six ways in the G8 GT.Our test model had the optional leather seats, and they were good-looking in black.The seats hold you tightly enough for sporty driving, although if you start playing Juan Pablo Montoya (this car can handle it, even if you can't), you'll feel a need for more bolstering.But if there were more, the car's appeal would narrow.

The instrumentation is good, although not without flaws.There's a digital battery and oil pressure gauge in the center of the dash that's unattractive and not particularly useful, and the digital transmission gear indicator is too small to read.The speedometer and tachometer are big enough, easy to read, and appropriate to the performance character of the G8.

The power window buttons are located between the seats, and we like them there.The emergency brake handle has been designed not to take up space, and it can be a grab handle, and that works too.The grab handles over the doors fit the hand and provide good leverage.

There's decent legroom in the rear seat, because this is a real sedan.The driveshaft tunnel doesn't intrude too much.There are heating and A/C vents back there, in the rear doors, where there are also speakers and good pockets, and front seatbacks have nets.The access to the trunk is wide.

The 6.0-liter overhead valve engine (like the engine in the Corvette) makes 361 horsepower and 385 pound-feet of torque, which peaks at a fairly high 4400 rpm, although the engine doesn't feel peaky.Overall, the GT feels trim.In fact, from the driver's seat, it feels smaller than it is.It has more power than any Pontiac in history (take that, you Firebird Trans-Am Ram Air big honkin' hood scoop muscle cars), but it's totally tame until you want to use that power.Then it will accelerate from 0 to 60 in 5.1 seconds and knock off the quarter-mile in 13.8.And with all that torque, the engine just lopes through places and situations that cause other sedans to take a harder swing.

But maybe the best thing about the all-new G8 is the six-speed transmission in the GT.Pontiac has joined the slim ranks of the savvy, by making a tight-shifting automatic transmission with manual control that's absolutely faithful to the driver's commands.It makes sport driving of the GT such a pleasure.

There are three modes to the Driver Shift Control transmission: Cruise, Sport and Manual.Cruise is fully automatic; Sport is automatic with more aggressive shift points, and Manual is, totally, manual.In Manual, it will short shift: that is, upshift under hard throttle but below redline.Sometimes that's a useful and smooth technique, and far too many automatic manual transmissions are programmed to disallow that; the thinking (by some engineer, somewhere) is that hard throttle means full speed means full revs.No, not necessarily.

The transmission employs rev matching for smoother downshifting, and the revs are just right.There are rational limits to the manual control, however: It won't let you downshift if the lower gear would cause the engine to reach redline where there's a rev limiter.But it will allow you to reach redline on the upshifts.It won't upshift for you, in manual mode, which you control with the lever.No paddle shifters, here.Not missed.

Cruise mode is true, too: for smooth cruising.You don't feel each downshift at every red light and stop sign.It understands gliding.

Sport mode is actually useful.Some aren't, because they just make the power delivery jerky.It can be an engineering tightrope walk, to find that happy medium between cruise and manual.It's a function of the programming and the engine characteristics.But it works with the GT.

However, Sport mode on the G8 with the V6 doesn't do much but make the shifts rougher.That's because the V6 and five-speed transmission lack the range of the V8 and six-speed.We got some good miles in the base G8, and through the twisties, in Sport mode, it kept kicking down like crazy.But it was smooth in Cruise, and true (and fun) in Manual.

The V6 is basically the same engine as in the Cadillac CTS, a 3.6-liter making 256 horsepower and 248 pound-feet of torque at a low 2100 rpm.The acceleration is good, but the exhaust note is raspy and not very pleasing, when you're hard on the throttle.On the freeway at steady light throttle, the engine is quiet.

Also, the suspension in the G8 doesn't have the same taut feel as in the GT.The variable-ratio, rack-and-pinion steering rates are different; also, the G8 brake rotors are smaller.The G8 is for those who love the style but don't really want the performance.It's less aggressive in every respect.It only gets one more highway mpg, but at least it runs on regular fuel, unlike the V8 which needs premium.

The 6.0-liter V8 engine (built in Mexico) uses active fuel management, which edges it up to its EPA rating of a combi.

Sam Moses filed this report to NewCarTestDrive.com after his test drive of the G8 models in Southern California.