Luxury Sedan Engine, Transmission, & Speed Comparison

The Caddy is a nice looker, too. It has perhaps one too many lines pressed into its sides, but is reasonably balanced and aging well. The new 17-in. wheels and tires really freshen things up. And talk about aging well: The Audi A8 is an example of exceptional balance and proportion. No cheap styling tricks required, it-like the rest of the Audi lineup-gives the impression that every inch and surface was designed with great care and restraint. Splicing in the extra five inches of wheelbase behind the B-pillar does nothing to upset the appearance. There's little question that the husky 18-in. AMG wheels and sportier fascia/rocker treatment that make up the S-Class' Sport package further enhance its substantial presence. But even without them, the Big Benz has a look that says luxury and power; it's much more balanced than its predecessor, and still gets people to notice. It's funny: If you look straight on at the noses of the S430 and the LS 430, you'll see they're definitions of the same theme; yet, to our eyes, the Mercedes looks both elegant and aggressive, while the Lexus appears, well, less so.

With 275 hp as the price of entry in this group, we knew we were in for solid performance from all six. We expected great things from the Q45's new 4.5L/340-hp V-8. Yet what we got were only good things. It's no slouch; 0-60 mph in 6.51 sec seems about par for this course. But it's no quicker than the 300-hp Cadillac, barely quicker (by just .06 sec) than the 310-hp Audi and slower than the 290-hp Lexus. Just to make sure, we tested a second car (a theoretically lighter base model), yet the results were effectively identical.

What's up? Many factors other than horsepower-an engine's power curve, transmission ratios, weight-affect ultimate performance. Either the Q doesn't quite crank out the horsepower at which it's rated, or the times were negatively affected by the engine-management system, which doesn't let the engine rev past about 1500 rpm while the brake pedal is depressed, inhibiting a hard launch. A few staffers didn't feel the transmission was particularly responsive, either, though the manumatic mode works nicely. The combo is smooth, quiet, and certainly delivers the goods at an impressive, if not world-beating, level; guess the big spec number just made us want more. We reviewed this situation with Infiniti, who claims the Q will run 0-60 in under six seconds. It was determined that both cars we tested were late run, pre-production vehicles, and Infiniti is quite certain that mainstream production cars will make good on its claim. We'll let you know as soon as we've arranged a re-test.

On the other hand, Mercedes' 4.3L V-8 doesn't feel appreciably slower than its 27-hp-stronger 5.0L big brother. But it is, at least enough to make it the slowest car of this group. It still sounds wonderful under load, silent when cruising and, unlike many Mercedes of the past, is ideally matched to its five-speed automatic. This transmission's TouchShift sequential action is by far the best of the bunch, allowing the most control, and quick, crisp up- or downshifts with just a light flick of the lever.

At the opposite end of the power scale comes the big bogie, in the form of Jaguar's supercharged V-8. We knew it would be the spoiler, and it is: 0-60 in 5.43, smooth full-power upshifts, blower wailing away. Nas-ty Kit-ty. The VP's antiquated J-gate feature spoils the euphoria, giving you only minimal control with a sloppy shifter that doesn't snap cleanly between the gates or even allow you to select first. This device should go the way of the dodo bird, now. But the engine's a keeper.

So is the new-for-2000 4.6L Northstar V-8 in the Seville. Despite being handicapped with one fewer ratio (a four-speed auto versus five in all the others), front drive (seldom the best for acceleration runs), and making its 300-hp on regular gas by design, the Caddy gets it done to 60 in 6.50 sec. And it sounds wonderful doing so, burbling out a distinctly American V-8 sound-with minimal torque steer. Less expensive to own, still fast.