Used 2007 Mercedes-Benz M-Class SUV

AMG didn't build its reputation for constructing manufacturer-warrantied engines with near racecar levels of output by going "easy." In 1999, an AMG-powered 349-horsepower ML55 held the super sport-utility crown alone — and many thought it was an absurd exercise in over-the-top engineering.

Now, in the ML63, AMG has produced a 503-hp all-wheel-drive sport-utility that has less than a handful of rivals: the 520-hp Porsche Cayenne Turbo S, 420-hp Jeep Grand Cherokee SRT8 and, to a lesser degree, the 355-hp BMW X5 4.8is and 320-hp Infiniti FX45. Where does the 2007 ML63 AMG stand in this unlikely super-ute spectrum?

What your money buys
When it's released this coming August, expect the five-seat all-wheel-drive ML63 AMG to fetch around $70,000. As of this writing, pricing, options and fuel-economy figures are not yet available. What we can tell you is that the naturally aspirated 503-hp, 6.2-liter V8 found in the ML63 is just one of the applications for this first ever AMG-designed engine, also found in the CLK63, CLS63, E63 and R63, with various output levels from 475-507 hp.

For a start, the big-bore, all-aluminum 6.2 shares no parts or dimensions with Mercedes-Benz-designed/supplied production V8 engines. Borrowing from AMG racing engine technology, the cylinder heads use bucket tappets instead of rocker arms and the engine block is a closed-deck design that includes cast-in steel reinforcements and a rigid "bedplate" instead of individual main bearing caps. According to AMG, the 6.2 features a first for production engines with its "twin-wire-arc-sprayed" cylinder walls that are twice as hard as conventional cast-iron liners. This really is the stuff of exotic racing engines.

The new V8 also includes the usual list of modern engine optimizations like an electronic throttle, four valves per cylinder, variable valve timing and variable-length intake runners. This is not a common engine, so don't expect to pay a common price for a vehicle that carries it, including the ML63 AMG.

All ahead full
Going on supplied specifications, the ML63 AMG boasts a 10.1 pound/hp weight-to-power ratio, nearly identical to the recently released 520-hp Porsche Cayenne Turbo S at 10.0 pound/hp. The comparison is a natural one; what that means is that AMG's claim of a 4.8-second run to 60 mph exactly matches the claim by Porsche, and both are completely within the realm of the possible. Coincidence? Our experience has shown both of these rivals' estimates are a bit conservative, and having driven both of them, we believe our inevitable full test of each will prove them even quicker.

But what distinguishes the ML63 from the Cayenne Turbo S is that AMG makes power the old-fashioned way — with more displacement, higher compression and a higher-revving V8 minus turbochargers. While the two super-utes offer the same results, they differ in the ways to get there. The power produced by the ML63's engine and taller gearing feels more like a slow but inevitable pull toward its 7,000-plus redline, whereas the Cayenne Turbo S surges like a pit bull tugging at its leash as each upshift occurs.

Coupled to the AMG-tuned seven-speed automatic transmission in Sport mode, the ML63 clicks off upshifts with the regularity of a metronome and the immediacy of a mouse click. If you'd prefer the Manual mode, the large buttons on the backside of the steering wheel work well for both up- and downshifting, as well. In normal conditions, the ML63's all-wheel-drive system distributes 40 percent of the driving power to the front axle and 60 percent to the rear, giving it a slight performance bias, and generally that works.

Damned Newton
Despite having large 295/40R20 Continental Cross Contact UHP tires, a sophisticated driveline and three-way-selectable suspension damping system, nothing can alter the fact that the ML63 is a tallish, 5,000-plus-pound vehicle that would prefer not to turn. Combine that reality with its slow-ratio steering and the AMG SUV is, indeed, better in a straight line than it could ever be around corners.

Admittedly, a thin layer of chalky silt dusted most of the winding roads for our drive so the conditions weren't racetrack-perfect, but the stability program's telltale yellow triangle was blinking like a third turn signal on most corner entries. The ML63 understeered resolutely into, through and even exiting sharp corners. Only when the front wheels were pointed more or less straight did the stability system relax its stranglehold on the progress of the ML63. Luckily, its vented and cross-drilled disc brakes complement the high-performance engine and scrub speed prior to those inconvenient corners.

And if you were wondering if the ML63 was a capable off-roader as well? In a word, no. There's no off-road package, low-range transfer case or skid-plate package.

A good deal?
If the $112,000 price tag of a Porsche Cayenne Turbo S is the standard for a 500-plus-hp midsize sport-utility that runs sub-5-second 0-60 times, then the ML63 is a deal. Or if the looks of the new 2006 M-Class are already too common, the AMG package distinguishes itself from a $48,500 ML500 with a unique grille, front- and rear-end fascias, flared fenders and (silly) stainless-steel running boards, along with special sport seats, an AMG steering wheel, napa leather upholstery and stainless-steel sport pedals.

Oh, and also included is a 503-hp V8. So there's that. As with any AMG-built vehicle, the engine is the product for which a customer pays, and whatever surrounds it is merely the wrapper. This new AMG-designed engine is a jewel to be proud of, and we believe it's only the beginning of more 6.2-liter variants on the way. We're also told the 6.2 fits under the hood of the C-Class. Can you imagine what AMG could do with a turbo- or supercharged version of an engine that starts with 475 hp? Going on its previous record, expect the E63 and CL63 to be the big guns carrying the maximum horsepower rating later this year. Now there's a story worth waiting for.