We've sampled the 3.9-liter V6 in other GM products, and it delivers a nice, broad power curve, with lots of acceleration-producing torque at all engine speeds. We'd also guess that in real-world driving, it will not produce a significant drop in Terraza's fuel mileage, compared to the standard 3.5-liter V6. The problem is that the 3.9 is only available in front-drive Terrazas. Until we can evaluate the new engine in this minivan, we can't offer snowbelt drivers a sound recommendation: all-wheel-drive, or front drive with the big V6.

Our hunch is that we'd take the bigger engine, even for places where the snow flies and the roads freeze. That's because that standard V6 is the weakest link in the Terraza package. If this Buick falls off compared to the best minivans, it's most obvious in the driving, and the single biggest reason is the engine.

The fundamental design of the cast-iron 3.5-liter V6 goes back decades, which doesn't necessarily mean it's bad. At interstate speeds the standard engine is quiet and relatively smooth. There's enough quick-burst acceleration for safe freeway merging or left turns during rush hour, and excellent transmission response helps take full advantage of the power that's available. GM makes some of the best automatic transmissions available anywhere. Terraza's has four speeds (compared to five in some competitors), but it responds quickly and appropriately to the driver's action on the gas pedal. It never hunts indecisively for the right gear, and shifts up or down as smooth as can be.

Given all that, the standard 3.5-liter V6 isn't likely to generate emotion of any sort, let alone a thrill. The numbers speak for themselves: Terraza's standard engine delivers less horsepower and torque than any in the class (except other GM minivans), and it's noticeable on the road. When it comes to high-rev power, smoothness or fuel economy, it can't match the overhead cam engines in some competitors, and it can't match the low-end grunt of cam-in-block engines in others. We recommend you test drive the 3.9-liter V6.

GM's VersaTrak fulltime all-wheel-drive system works very well in snow, slush and ice, and we heartily recommend it. VersaTrak's mechanicals are relatively simple, and add less weight to the vehicle than many all-wheel-drive systems. There are no buttons or levers to engage, yet in operation VersaTrak can do things some similar systems can't. When the Terraza's front wheels lose grip, the system automatically shifts engine power to the rear wheels, greatly improving the odds of continued forward mobility. Yet VersaTrak can also shift power from side to side between the rear wheels. If the inside wheel encounters slush build-up near the center of the road, VersaTrak sends power to the outside wheel with grip.

Front-wheel-drive Terrazas come standard with StabiliTrak, GM's electronic stability system. This is valuable, too. Let's say a driver inadvertently drops the right-side wheels off the pavement and onto a gravel shoulder. The right-side wheels would tend to lose grip on the low-friction gravel. Without StabiliTrak, the left-side wheels would continue to grip as before, quite possibly directing the vehicle toward the center line or opposite lane. StabiliTrak senses the disparity in traction and intervenes by applying brakes to the outside wheels or cutting engine power. The electronics help prevent a sharp change in direction and help the driver to regain full control without overreacting or overcorrecting. In short, StabiliTrak can help you avoid a wreck.

StabiliTrack is offered only on front-drive models. It's not available with all-wheel drive. In the northeast or mountain states, we'd choose the all-wheel drive. It brings a slight penalty in fuel mileage (1 mile per gallon according to EPA figures), but in the right climate it's well worth it. Unfortunately, with a new upgrade V6 engine option for 2006, the all-wheel-drive/electronic stability program decision gets more difficult, and in this case we aren't able to make a clear recommendation.

Ride quality is comfortably soft, but it comes with side-to-side sway in corners taken at any speed faster than sedate. The steering is very light, and great for negotiating parking lots, but it doesn't offer much road feel, so it doesn't tell a driver much about how the front tires are gripping. On back roads, the Terraza does not respond as crisply as some other minivans. Some drivers may appreciate the softer ride and never know the handling difference.

Most drivers will appreciate the quiet inside. Terraza benefits from what Buick calls Quiet Tuning: a package of sound blockers, attenuators, and deadeners from the firewall to the tailgate. Considering the size of the hole the Terraza cuts through the air, the big tires and the huge glass area, it is very quiet at all speeds on good pavement (though the suspension can clunk a bit on rough stuff). Any minivan, because it is essentially a big empty box with lots of glass, is an acoustic engineer's nightmare, and Buick has done a world-class job of quieting things down.

The brakes work impressively, too. In full-on stops, the Terraza's anti-lock braking system keeps the wheels precisely at the point of lockup without any shuddering through the pedal, and stops this minivan as quickly as possible while leaving the driver full directional control. The 25-gallon fuel tank is another plus. Based on our real-world mileage figures, highway range of more than 550 miles is within reach.