Comparison Test: 2009 Mercedes-Benz ML320 Bluetec vs. 2008 Lexus RX 400h

2009 Mercedes-Benz M-Class SUV

(3.0L V6 Turbo Diesel AWD 7-speed Automatic)
  • 2009 Mercedes-Benz ML320 Bluetec vs. 2008 Lexus RX 400h Comparison Test Video

    Watch the 2009 Mercedes-Benz ML320 Bluetec vs. 2008 Lexus RX 400h Comparison Test Video on Edmunds’ Inside Line | September 25, 2009

1 Video , 29 Photos

Diesel Vs. Hybrid: We Debate Two Technologies

  • Comparison Test
  • Second Opinion
  • Top 8 Features
  • Data and Charts
  • Final Rankings and Scoring Explanation
  • 2008 Lexus RX 400h Specs and Performance
  • 2009 Mercedes-Benz M-Class Specs and Performance

Diesel Vs. Hybrid: We Debate Two Technologies

Sure, you can get sticker shock at the gas station, but you don't have to give up your sport-utility vehicle. You don't even have to give up the carlike luxury trimmings you've come to expect as part of the SUV experience.

That's what the 2009 Mercedes-Benz ML320 Bluetec and 2008 Lexus RX 400h are meant for.

Or maybe you're looking to make a political statement. Those on the right-hand side of the aisle might want to use less imported oil, while left-leaning types just want to use less oil, period. And what better way to represent your social consciousness than with the SUV you drive?

In fact, this comparison is all about the debate. Once you commit to a greener way of life with a sport-utility, which is the better choice, diesel or hybrid? 2009 Mercedes-Benz ML320 Bluetec or 2008 Lexus RX 400h?

Point, Counterpoint
Representing the left is the progressive 2008 Lexus RX 400h — that's "h" as in hybrid. This RX features a beefier version of the Hybrid Synergy Drive system found in that darling of the eco-warrior set, the Toyota Prius. Depending on how hard you leg it, the RX 400h's gasoline-fueled 3.3-liter V6 plus its assemblage of electric motors and batteries can either put 268 horsepower to the pavement or return 25 mpg combined — 6 mpg more than a non-hybrid RX 350.

On the right is the more traditional and conservative 2009 Mercedes-Benz ML320 Bluetec, powered by a 3.0-liter V6 turbodiesel that pumps out 398 pound-feet of torque. The inherent efficiency of the diesel cycle means the ML320 Bluetec is rated at 21 mpg on the EPA's combined cycle, some 24 percent more than the otherwise identical gasoline-powered Mercedes ML350.

Ah, but this is no old-school soot-belching diesel. The Bluetec moniker identifies this ML320 as a diesel that meets the same tailpipe emissions standards required of gasoline engines sold in California — the toughest such diesel regulations in the world.

The Bluetec system combats oxides of nitrogen (NOx), the nasty byproduct of the diesel combustion cycle, by employing two catalytic converters. AdBlue, an aqueous urea solution stored aboard the Benz in a separate tank, is injected into a downstream exhaust catalyst where it reacts with the NOx in a process known as Selective Catalytic Reduction to form harmless nitrogen and water vapor.

Price and Prejudice
The price of our 2008 Lexus RX 400h, an all-wheel-drive model, starts at $44,305. When you pay $4,130 more, you get an integrated system that includes navigation, Mark Levinson premium audio, Bluetooth and a rearview camera. The interface is supremely easy to use and understand, but frankly we're baffled at the absence of even the most basic auxiliary jack to connect an iPod or MP3 player. Nostalgia fans may appreciate the included cassette deck, but we're not amused.

The RX's interior materials are very good, but the overall environment doesn't express luxury values quite like the Benz. The leather seats that come with the $1,600 premium package are soft enough, but the $380 trim in black bird's eye maple looks somehow inorganic.

Add $665 more for heated front seats and rain-sensing wipers and another $160 for the towing prep package (cooling system upgrades, not a hitch) and you arrive at this RX 400h's $50,885 as-tested sticker price.

The 2009 Mercedes-Benz ML320 diesel's price tag starts at $48,125 and quickly heads north. You'll pay $6,600 for Premium Package #2, consisting of navigation, Harmon Kardon premium audio that includes iPod and memory card inputs, Bluetooth, a rearview camera, proximity sensors and a host of power luxuries. We're not overly fond of single-point control strategies like Mercedes' COMAND system, but here it's nearly intolerable. The well-weighted control wheel found in our 2007 Mercedes-Benz C300 Sport long-term test car is absent, replaced here by a circular array of five flat buttons positioned on the passenger side of the center stack.

But there is no denying the high cush-factor that exudes from all the surfaces of the interior. Our test ML has $1,995 of gorgeous leather seats and exquisite wood interior trim, and every detail suggests a high level of craftsmanship. The $1,390 heating package includes heated front and rear seats and even a heated steering-wheel rim. A third zone of automatic climate control for the rear seat passengers costs $770. And then the whole thing is lathered in Alpine Rain metallic paint, a $720 option.

Of course, then you add another $1,600 for height-adjustable air suspension with adaptive damping. So the final damage on this luxuriously equipped utility vehicle is $61,200.

On the Move
We've driven Lexus RX hybrids before, and this one is much as we remember. Instantly accessible torque from the electric motor provides a good shove when you leave the line at a stoplight, as our 7.2-second acceleration to 60 mph (6.8 seconds with 1 foot of rollout like on a drag strip) can attest. In town, the computer-regulated transition from electric to gasoline motivation is seamless, and power flows smoothly through the shiftless planetary continuously variable transmission (CVT).

The braking performance of this Lexus, on the other hand, is decidedly average, as it takes a ho-hum 133 feet to come to a halt from 60 mph and the body dives noticeably. Speaking of hum, you'll hear a melodious hint of it from the regenerative braking system as it feeds power back to the batteries, especially when you ease to an unhurried stop. Think of it as the sound of fuel savings and maybe you won't be bugged by the annoying transition from regen braking to full mechanical retardation while you're in stop-and-go traffic.

The electric power steering is accurate enough, but the effort doesn't build much as the tires load up with cornering force, lending a somewhat numb feel. These fuel-friendly low-rolling-resistance tires also fail to generate much grip — just 0.68 lateral g on our skid pad — so the RX 400h's stability control system fires early in spirited driving.

On Your Right
The personality of the Mercedes-Benz ML320 Bluetec is about 180 degrees opposite to that of the Lexus. There is a slight hesitation when you jab the throttle pedal, but shortly thereafter the turbo boost builds, the torque comes on line and the big Merc accelerates smoothly through its seven-speed transmission. Our ML weighs 5,129 pounds, some 610 pounds more than the RX. As a result, its somewhat pedestrian acceleration to 60 mph in 8.5 seconds (8.2 seconds with 1 foot of rollout, like on a drag strip) is expected.

This extra mass doesn't seem to hamper stopping distance, as the Benz needs only 121 feet to halt from 60 mph. Wider 255/50R19 tires — more than an inch broader than the Lexus — doubtlessly play a role here. Bigger shoes also improve grip, and the heavier Merc posts 0.76 g on the skid pad and negotiates our slalom at 62.6 mph (a full 3 mph faster than the Lexus). There's more steering feedback, too, but the softly sprung air suspension lets the body roll too eagerly as you turn into a corner.

And that's not all. The use of air suspension also gives the ML a queasy ride, as it rocks a bit too easily from side to side over uneven pavement (the wife of one of us even vetoed a planned trip into the mountains after getting nauseous during a simple freeway cruise). Flicking the adaptive damping to Sport mode doesn't entirely quell the underlying floaty nature of the suspension; instead, it merely layers the occasional harsh jolt over the top.

We never thought we'd say this, but the smooth-riding Lexus feels taut and well-damped compared to the Benz. We recommend that ML shoppers save $1,600 and give the standard coil-spring suspension some serious consideration.

Utility Is the Middle Name
Both these SUVs lack the option of a third row, a state of affairs that allows both to optimize seat room for rear occupants. The Benz scores higher here, because its longer wheelbase (114.7 inches vs. 106.9) gives it a 3.6-inch advantage in rear-seat legroom. The Lexus has plenty, but the Mercedes seems like a presidential limo back there.

You'd think that the Benz would enjoy a cargo space advantage, too, but that doesn't appear to be the case. Lexus boasts that 84.7 cubic feet is available with the seats down in the RX, while Benz only claims 72.4 cubic feet of maximum cargo space. We suspect the Benz number assumes a conservative loading strategy that maintains sight lines out the rear window.

Both candidates offer all-wheel drive, but their systems differ dramatically. The RX 400h only has on-again, off-again electric motor power that goes to the rear axle, as the gas engine and CVT supply power exclusively to the front wheels. This means that the Lexus isn't suitable for off-road duty; its AWD system is best seen as a traction aid on snow-covered roads. Meanwhile, the ML has Benz's 4Matic always-on all-wheel-drive system with three differentials, electronically activated (through the ABS system) limited-slip action, as well as hill descent control. The ML doesn't have a low-range transfer case, so you can't take it to the Rubicon Trail, but you can take it off-road.

Towing is a huge area of difference between the hybrid and the diesel. Even with the towing prep pack, the RX 400h is rated for only 3,500 pounds of towing capacity. That's good for a couple of motorcycles or watercraft, but camping trailers and car haulers are out of its league. The ML320 Bluetec, on the other hand, is rated for 7,200 pounds of towing capacity — some serious capacity. Plus, a diesel usually preserves much more of its fuel economy while towing than a gasoline engine, too.

The Catch
But there's a problem with the Benz: It's got no spare tire. Why? The all-important AdBlue fluid tank has to go somewhere, and the only available spot apparently is the space under the cargo floor that usually accommodates a spare tire.

No spare means the ML320 Bluetec wears run-flat tires. Run-flats might sound like a great idea; nobody need worry about stopping on the side of a freeway or in a bad neighborhood (one without a Starbucks, presumably) if a tire goes flat. But finding an exact replacement run-flat tire within 100 miles of a tire failure isn't always easy in this massive country of ours. And they're not cheap to replace.

That's the car argument. For SUVs, the situation is even more critical. With the ML you could find yourself 30 miles down a dirt road or camping in a remote spot. Maybe you suffer your flat when visiting the north rim of the Grand Canyon with your 25-foot camping trailer in tow. The nearest city with a chance of having a replacement Bridgestone Dueller H/L 400 is Las Vegas, 266 miles away. Guess what? The run-flat range of an ML320 loaded to GVWR is only 20 miles. What do you do then?

We think that if you plan to use your SUV as an SUV, then you should have a spare tire — period.

The Results Are in
For most of our test, the 2009 Mercedes-Benz ML320 Bluetec led the Lexus in our comparison. Sure it's more expensive, but the level of equipment and the luxury feel of the cabin justifies the price. The diesel powertrain might not be quite as fuel-efficient as the RX in town, but it still delivers good urban fuel consumption numbers for a vehicle of its size, while its highway fuel economy is the same as the RX and its overall cruising range is superior. It even handles well (especially considering its 7,200-pound tow rating).

But the limited safety margin offered by the Benz's run-flat spare negates its adventure capability because we can't in good conscience recommend that you tow or go off-road without a spare. So what we're left with, then, is a comparison of two pavement-bound SUVs that are meant for the suburbs.

And on that basis, the 2008 Lexus RX 400h comes out ahead in this comparison. For thousands of dollars less, it's a well-equipped, smooth-riding luxury SUV with seamless power delivery, and it just happens to use less fuel than any garden-variety compact SUV. And isn't that the point of this debate anyway?

The manufacturers provided Edmunds these vehicles for the purposes of evaluation.

Edmunds.com Associate Editor Josh Sadlier says:
The RX 400h's platform debuted way back in 2004, which is eons ago in car years. I still dig the exterior styling, but the cabin is really starting to show its age, from the tacky silver-painted plastic on the center stack to the featureless front seats with minimal power adjustments. Sure, the Benz costs an additional $10 grand as tested, but its sumptuous interior makes that premium seem almost reasonable.

But if I had to choose between them, I'd take the Lexus every day of the week.

The Benz's Bluetec engine is supposed to be the big news here — a clean-burning diesel that meets 2010 emissions standards while theoretically providing that classic diesel combination of fuel-efficiency and low-end kick. Yet the RX 400h's aging hybrid powertrain smokes the Benz's like a puff of old-school diesel exhaust. Sixty mph arrives more than a second sooner in the Lexus, and its responsive CVT delivers a heady rush of electrically assisted power on demand. The RX trounced the ML320 in observed fuel economy, too, and the premium gas it requires is about 30 cents cheaper than diesel as of this writing.

In other words: Diesel, schmiesel. And the Lexus steers better to boot. Make that much better — the RX's electric power steering system is slop-free and nicely weighted, while the Benz's gooey hydraulic setup feels about as precise as the helm of a commercial fishing vessel. These vehicles aren't built with enthusiasts in mind, of course, but if you enjoy driving, there's only one horse in this race.

Yes, the Lexus feels old. But it's both quicker and more fuel-efficient than the Benz, its steering is superior, it's considerably cheaper, and oh yeah — its concert-quality Mark Levinson stereo puts the Merc's Harman Kardon system to shame. I'll certainly stay tuned as the Bluetec lineup evolves, but for now, the hoary Lexus hybrid reigns supreme.

The Mercedes-Benz ML320 Bluetec and the Lexus RX 400h are both premium SUVs, yet the as-tested prices of our test vehicles differed by more than $10,000. And their basic layouts differ quite a bit, too. The Benz is a diesel-powered SUV in a dedicated unit-body chassis, while the RX combines a hybrid powertrain with a crossover chassis. Although a surprising number of items on the as-tested option sheets of these vehicles are similar, there are some significant differences.

Features

Features
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Engine-off electric propulsion mode and regenerative brakes S N/A
Full-time all-wheel drive N/A S
Heated rear seats and steering wheel N/A O
Height-adjustable air suspension N/A O
iPod and aux jack inputs N/A S
Metallic paint S O
Power glass sunroof O S
Spare tire S N/A


Key:
S: Standard
O: Optional
N/A: Not Available

Engine-off electric propulsion mode and regenerative brakes: This is the technical way of defining a hybrid powertrain. These operating modes are the key to real fuel savings, as they recover lost energy for later use. There is nothing that says a diesel engine cannot be connected to such a system, but the ML320 is not.

Full-time all-wheel drive: Superior traction on dirt, pavement and snow is made possible by full-time all-wheel drive. The ML's system is always engaged, has three differentials to distribute torque and is bolstered by an ABS-based traction control system to prevent wheelspin. The Lexus hybrid's rear axle is powered entirely by electricity and isn't connected to the V6 engine at all, so it is not really an off-road-capable system.

Heated rear seats and steering wheel: Front heated seats are expected in this class. But for this kind of money, rear heated seats should be on the options sheet. The Benz offers them — plus a heated steering wheel rim — but the RX 400h does not.

Height-adjustable air suspension: Air suspension allows an SUV to raise and lower itself to suit conditions. Such a system is available on the ML320, but is not on the Lexus options sheet.

iPod and aux jack inputs: The most basic auxiliary input jack is commonplace at price points much lower than this. Fully compatible iPod connections with full integration into the stereo head unit are also on the rise. The 2009 ML320 Bluetec features both, but the 2008 Lexus RX 400h has neither.

Metallic paint: Metallic paint colors are standard on the Lexus RX 400h, but the metallic paint on our ML320 Bluetec is a $720 option.

Power glass sunroof: This is a popular feature that needs no further explanation. You have to pay extra to get one in the Lexus, but it comes standard on the ML320.

Spare tire: This sounds pretty low-tech to be included here, but these are SUVs. The Benz boasts superior off-road and towing ability, but the lack of a spare tire (it features run-flat tires) makes such journeys inadvisable. The Lexus makes no such outdoorsy claims, but it does have a spare.

Dimensions
Engine & Transmission Specifications
Warranty Information
Performance Information
Crash Test Scores


Dimensions

Exterior Dimensions & Capacities
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Length, in. 187.2 188.5
Width, in. 72.6 75.2
Height, in. 68.5 71.5
Wheelbase, in. 106.9 114.7
Manufacturer Curb Weight, lb. 4,365 4,974
Turning Circle, ft. 37.4 37.9
Tire size P225/65R17 255/50R19
Wheel type 17-inch alloy 19-inch alloy
Interior Dimensions
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Front headroom, in. 39.4 39.9
Rear headroom, in. 37.5 39.8
Front shoulder room, in. 57.9 59.8
Rear shoulder room, in. 57.1 59.8
Front legroom, in. 42.5 42.2
Rear legroom, in. 36.4 40.0
Cargo volume, cu-ft. 38.3 54.7
Max cargo volume, cu-ft. 84.7 72.4

Engine & Transmission Specifications

Engine & Transmission
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Displacement (cc / cu-in): 3,311 (202) 2,987 (182)
Engine Type V6 gasoline V6 turbodiesel
Horsepower (SAE) @ rpm 208 @ 5,600 210 @ 3,800
Max. Torque, lb-ft @ rpm 212 @ 4,400 398 @ 1,600-2,400
Electric motor output, hp @ rpm Fr: 167 @ 4,500 Rr: 68 @ 4,610-5,120
Electric motor max.torque, lb-ft @ rpm Fr: 247 @ 0-1,500 Rr: 96 @ 0-610
System voltage (max.) 650
Battery peak power rating (hp) 60
Max. blended horsepower 268
Transmission Planetary CVT 7-speed automatic
EPA Fuel Economy City, mpg 26.0 18.0
EPA Fuel Economy Hwy, mpg 24.0 24.0
Observed fuel economy Suburban city loop mpg 29.2 20.3
Observed Fuel Economy Edmunds combined, mpg 24.6 21.2
Fuel tank capacity, gal. 17.2 25.1

Warranty

Warranty Information
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Basic Warranty 4 years/50,000 miles 4 years/50,000 miles
Powertrain 6 years/70,000 miles 4 years/50,000 miles
Roadside Assistance 4 years/Unlimited miles Unlimited
Corrosion Protection 6 years/Unlimited miles 4 years/50,000 miles
Hybrid Battery* 8 years/100,000 miles 10 years/150,000 miles N/A
*tied to mandated emissions warranties, which vary between federal and CA emissions states

Performance

Performance Information
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
0-60 mph acceleration, sec. 7.2 8.5
Quarter-mile acceleration, sec. 15.2 16.2
Quarter-mile speed, mph 92.2 83.3
60-0-mph braking, feet 133 121
Lateral Acceleration, g 0.68* 0.76*
600-ft slalom, mph 59.6* 62.6*

*electronically limited by ESC

Safety

Safety Information
2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Front airbags Standard Standard
Side airbags Standard dual front Standard dual front and rear
Head airbags Standard front and rear curtain Standard front and rear curtain
Antilock brakes 4-wheel ABS 4-wheel ABS
Traction control Standard Standard
Stability control Standard Standard
Tire pressure monitoring Direct measurement Direct measurement
NHTSA frontal crash, driver 5 stars 5 stars
NHTSA frontal crash, passenger 5 stars 5 stars
NHTSA side crash, driver 5 stars 5 stars
NHTSA side crash, passenger 5 stars 5 stars
NHTSA rollover resistance Not tested 4 stars
IIHS offset crash Good Good

Final Rankings

Final Rankings
Item Weight 2008 Lexus RX 400h AWD 2009 Mercedes-Benz ML320 Bluetec
Personal Rating 2.5% 100.0 50.0
Recommended Rating 2.5% 100.0 50.0
Evaluation Score 15% 74.5 76.9
Feature Content 15% 45.8 66.7
Performance 15% 86.8 84.9
Fuel Consumption 25% 100.0 81.0
Price 25% 100.0 79.7
Total Score 100.0% 86.1 77.0
Final Ranking 1 2
$50,885 $61,200

Personal rating (2.5%): Purely subjective. After the test, each participating editor was asked to rank the vehicles in order of preference based on which he or she would buy for his or her own use.

Recommended rating (2.5%): After the test, each participating editor was asked to rank the vehicles in order of preference based on which he or she thought would be best for the average consumer shopping in this segment.

30-point evaluation (15%): Each participating editor ranked both vehicles using a comprehensive 30-point evaluation process. The evaluation covered everything from exterior design to cupholders. Scoring was calculated on a point system, and the scores listed are averages based on all test participants' evaluations.

Feature content (15%): Editors picked eight significant distinguishing features they thought would be most beneficial to a consumer shopping in this segment. Each test vehicle was then given a score based on which of those features it possessed. More points were awarded when these features were standard versus optional, and no points were given if the feature was unavailable on a given vehicle. The score given here represents the percentage of points, out of a total possible 24 points.

Performance testing (15%): We subjected these cars to our standard set of performance tests. Scores were calculated by giving the best car in each specific performance category 100 percent. The subsequent vehicle was awarded points based on how close it came to the best performing vehicle's score.

Fuel Consumption (25%): Fuel consumption is an important purchase reason, especially in these two vehicles, so this category was weighted heavily. Using EPA combined fuel economy ratings as the basis for comparison, we awarded a score of 100 percent to the most fuel-efficient vehicle. The less-efficient vehicle was awarded points based on how close it came to the best-performing vehicle's fuel consumption.

Price (25%): The numbers listed were the result of a simple percentage calculation based on the less expensive vehicle in the comparison test. Using the "as tested" prices of the actual evaluation vehicles, the less expensive vehicle received a score of 100, with the remaining vehicle receiving a lesser score based on how much it costs.

Vehicle
Model year2008
MakeLexus
ModelRX 400h
Style4dr SUV AWD (3.3L 6cyl gas/electric hybrid CVT)
Base MSRP$44,305
Options on test vehicleNavigation System/Mark Levinson Package ($4,130); Premium Package ($1,245); Heated Front Seats With Rain-Sensing Wipers ($665); Genuine Wood Interior Trim ($380); Towing Prep Package ($160).
As-tested MSRP$50,885
Drivetrain
Drive typeFront-wheel gasoline-electric hybrid drive supplemented by on-demand electric rear-wheel drive.
Engine typeV6, Atkinson cycle
Displacement (cc/cu-in)3,311cc (202 cu-in)
Block/head materialAluminum
ValvetrainDOHC, 4 valves per cylinder, variable valve timing
Compression ratio (x:1)10.8:1
Redline (rpm)5,600
Horsepower (hp @ rpm)208 @ 5,600 (gasoline engine); 268 when blended with the electric motors
Torque (lb-ft @ rpm)212 @ 4,400 (gasoline engine); 247 @ 0-1,500 (front electric motor); 96 @ 0-610 (rear electric motor)
Transmission typePlanetary CVT
Chassis
Suspension, frontIndependent, MacPherson struts, coil springs and stabilizer bar
Suspension, rearIndependent, MacPherson struts, coil springs and stabilizer bar
Steering typeElectric power steering
Steering ratio (x:1)15.6:1
Tire brandMichelin
Tire modelEnergy LX4
Tire typeAll-season
Tire size, front225/65R17 101S
Tire size, rear225/65R17 101S
Wheel size17-by-6.5 inches front and rear
Wheel materialAluminum alloy
Brakes, front12.6-inch ventilated disc
Brakes, rear11.3-inch disc
Track Test Results
0-45 mph (sec.)4.7
0-60 mph (sec.)7.2
0-75 mph (sec.)10.3
1/4-mile (sec. @ mph)15.2 @ 92.2
0-60 with 1 foot of rollout (sec.)6.8
Braking, 30-0 mph (ft.)35
60-0 mph (ft.)133
Slalom, 6 x 100 ft. (mph)59.6
Skid pad, 200-ft. diameter (lateral g)0.68
Sound level @ idle (dB)31.8 (electric mode, engine off)
@ Full throttle (dB)73.6
Test Driver Ratings & Comments
Acceleration commentsPrior to the first run, I gathered as many battery bars (on the display) as possible. Launch is enhanced by brake torque to wake up the internal combustion engine, and it gets off the line quickly. Obviously, seamless transmission makes the most of the combined output, pegging the electric motors' contribution. Slight tire nibble just shy of what I'd call torque steer.
Braking ratingAverage
Braking commentsSome delay between mashing the brake pedal and actual slowing. Once engaged, ABS is pretty quiet and shudder-free. No noticeable fade in pedal or distances. Noticeable body pitch.
Handling ratingAverage
Handling commentsSkid pad: Non-defeat VSC limits performance. Contrary to most Toyota systems, however, the RX's grabs the brakes before the warning beeps begin. Steering doesn't load much and borders on numb. Slalom: Again the VSC limits the RX's performance, but there's still quite a lot of agility here. Steering is light and precise, body roll is pronounced but grip is trustworthy. In the end, I could sense the weight of this vehicle and the VSC clamps down right before it gets away from itself.
Testing Conditions
Elevation (ft.)421
Temperature (°F)85.7
Wind (mph, direction)5.3
Fuel Consumption
EPA fuel economy (mpg)26 city/24 highway
Edmunds observed (mpg)24.6
Fuel tank capacity (U.S. gal.)17.2
Dimensions & Capacities
Curb weight, mfr. claim (lbs.)4,365
Curb weight, as tested (lbs.)4,519
Weight distribution, as tested, f/r (%)57/43
Length (in.)187.2
Width (in.)72.6
Height (in.)66.4
Wheelbase (in.)106.9
Track, front (in.)62
Track, rear (in.)61.2
Turning circle (ft.)37.4
Legroom, front (in.)42.5
Legroom, rear (in.)36.4
Headroom, front (in.)39.4
Headroom, rear (in.)37.5
Shoulder room, front (in.)57.9
Shoulder room, rear (in.)57.1
Seating capacity5
Cargo volume (cu-ft)38.3
Max. cargo volume, seats folded (cu-ft)84.7
Warranty
Bumper-to-bumper4 years/50,000 miles
Powertrain6 years/70,000 miles
Corrosion6 years/Unlimited miles
Roadside assistance4 years/Unlimited miles
Free scheduled maintenanceUnlimited within the first 5,000 miles
Safety
Front airbagsStandard
Side airbagsStandard dual front
Head airbagsStandard front and rear
Knee airbagsDriver only
Antilock brakes4-wheel ABS
Electronic brake enhancementsBraking assist, electronic brakeforce distribution
Traction controlStandard
Stability controlStandard
Rollover protectionStandard
Tire-pressure monitoring systemTire-pressure monitoring
Emergency assistance systemNot Available
NHTSA crash test, driver5 stars
NHTSA crash test, passenger5 stars
NHTSA crash test, side front5 stars
NHTSA crash test, side rear5 stars
NHTSA rollover resistanceNot tested
Vehicle
Model year2009
MakeMercedes-Benz
ModelM-Class
StyleML320 Bluetec 4dr SUV AWD (3.0L 6cyl Turbodiesel 7A)
Base MSRP$48,125
Options on test vehiclePremium Package #2 ($6,600); Full Leather Seating Package ($1,995); Airmatic Suspension With Adaptive Damping System ($1,600); Heating Package ($1,390); 3-Zone Automatic Climate Control ($770); Alpine Rain Metallic Paint ($720).
As-tested MSRP$61,200
Drivetrain
Drive typeAll-wheel drive with low range
Engine typeV6 turbocharged diesel
Displacement (cc/cu-in)2,987cc (182 cu-in)
Block/head materialAluminum with cast iron cylinder liners/aluminum
ValvetrainDOHC, 4 valves per cylinder, variable valve timing
Compression ratio (x:1)16.5:1
Redline (rpm)4,500
Horsepower (hp @ rpm)210 @ 3,800
Torque (lb-ft @ rpm)398 @ 1,600-2,400
Transmission type7-speed automatic
Transmission and axle ratios (x:1)I = 4.38; II = 2.86; III = 1.92; IV = 1.37; V = 1.00; VI = 0.82; VII = 0.73; Final Drive = 3.45
Chassis
Suspension, frontIndependent, double wishbones, pneumatic springs and stabilizer bar
Suspension, rearIndependent, multilink, pneumatic springs and stabilizer bar
Steering typehydraulic power steering
Steering ratio (x:1)18.6:1
Tire brandBridgestone
Tire modelDueler H/L 400
Tire typeAll-season, run-flat
Tire size, front255/50R19 107N
Tire size, rear255/50R19 107N
Wheel size19-by-8.0 inches front and rear
Wheel materialAlloy
Brakes, front13.0-by-1.26-inch ventilated disc
Brakes, rear13.0-by-0.55-inch disc
Track Test Results
0-45 mph (sec.)5.1
0-60 mph (sec.)8.5
0-75 mph (sec.)13.1
1/4-mile (sec. @ mph)16.2 @ 83.3
0-60 with 1 foot of rollout (sec.)8.2
Braking, 30-0 mph (ft.)31
60-0 mph (ft.)121
Slalom, 6 x 100 ft. (mph)62.6
Skid pad, 200-ft. diameter (lateral g)0.76
Sound level @ idle (dB)45.8
@ Full throttle (dB)68.6
@ 70 mph cruise (dB)64.7
Test Driver Ratings & Comments
Acceleration commentsResponds extremely well to brake torque to the tune of 0.6 second to 30 mph. It leaps off the line like a Nissan GT-R, but then realizes it's a turbodiesel. Transmission is busy due to the low redline, but pretty smooth shifting.
Braking ratingGood
Braking commentsSoft-ish pedal in normal use goes rock-hard under full-ABS. Even with the suspension on the firmest setting, there's quite a lot of pitch. More tire noise than ABS noise. Admirable power in the system and good fade resistance, too.
Handling ratingGood
Handling commentsSkid pad: Extended-range ESP is still limiting performance as the outside front tire gets abused. Steering gets noticeably heavier when loaded. Slalom: Limit of the chassis is right up against the extended ESP setting so it only intrudes if it's a sloppy run. Keeping inputs smooth and to a minimum is the quickest way through. Grip and body motions are admirably good for such a tall and heavy vehicle.
Testing Conditions
Elevation (ft.)421
Temperature (°F)87.6
Wind (mph, direction)5.4
Fuel Consumption
EPA fuel economy (mpg)18 city/24 highway
Edmunds observed (mpg)21.2
Fuel tank capacity (U.S. gal.)25.1
Dimensions & Capacities
Curb weight, mfr. claim (lbs.)4,974
Curb weight, as tested (lbs.)5,129
Weight distribution, as tested, f/r (%)54/46
Length (in.)188.5
Width (in.)75.2
Height (in.)71.5
Wheelbase (in.)114.7
Track, front (in.)64
Track, rear (in.)64.1
Turning circle (ft.)37.9
Legroom, front (in.)42.2
Legroom, rear (in.)40
Headroom, front (in.)39.9
Headroom, rear (in.)39.8
Shoulder room, front (in.)59.8
Shoulder room, rear (in.)59.8
Seating capacity5
Cargo volume (cu-ft)54.7
Max. cargo volume, seats folded (cu-ft)72.4
Warranty
Bumper-to-bumper4 years/50,000 miles
Powertrain4 years/50,000 miles
Corrosion4 years/50,000 miles
Roadside assistanceUnlimited
Free scheduled maintenanceInitial visit within first 3,000 miles
Safety
Front airbagsStandard
Side airbagsStandard dual front and dual rear
Head airbagsStandard front and rear
Knee airbagsNot available
Antilock brakes4-wheel ABS
Electronic brake enhancementsBraking assist, electronic brakeforce distribution
Traction controlStandard
Stability controlStandard
Rollover protectionStandard
Tire-pressure monitoring systemDirect tire-pressure monitoring
Emergency assistance systemPre-collision safety system
NHTSA crash test, driver5 stars
NHTSA crash test, passenger5 stars
NHTSA crash test, side front5 stars
NHTSA crash test, side rear5 stars
NHTSA rollover resistance4 stars
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Edmunds Insurance Estimator

The Edmunds TCO® estimated monthly insurance payment for a 2009 Mercedes-Benz M-Class in WA is:

$183 per month*
* Explanation
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