Acceleration

GL320 CDI	GL450	GL550	Class Average
5	6	7	5.9

Both V8s deliver effortless thrust, and while the GL550 has more punch, the GL450 is plenty strong for any task.

The 320 CDI version can feel slightly lethargic off the line, and some testers want quicker highway passing response, but its turbodiesel V6 never feels underpowered. All engines benefit from a smooth, alert automatic transmission.

Fuel Economy

GL320 CDI	GL450	GL550	Class Average
5	4	3	2.3

In Consumer Guide testing, a GL450 averaged 16.4 mpg in an even mix of city/highway driving. We've had no opportunity to measure fuel economy with other GL models. The V8s require premium-grade gas. Note that CDI models are not sold in California and certain Northeastern states.

Ride Quality

GL320 CDI	GL450	GL550	Class Average
6	6	5	6.4

The GL320 CDI and GL450 with the standard 18-inch tires are impressively compliant over bumps. When equipped with the optional 19-inch tires, those models, like the GL550 with its 21s, can't absorb sharp ridges without some jarring. All are stable at speed but also sway and rock more than optimal on uneven surfaces.

Steering/Handling/Braking

GL320 CDI	GL450	GL550	Class Average
5	5	5	4.2

Steering is accurate and direct. The GL550, however, tends to tramline along channels in the road and can skitter sideways in bumpy corners, compromising the sure-footed security of the other GLs. In fast turns on smooth surfaces, the GL550 has tenacious grip and relatively little body lean, but all GLs stay flatter in corners than most large SUVs. One test GL450 had a mushy brake-pedal feel.

Quietness

GL320 CDI	GL450	GL550	Class Average
8	8	7	6.8

These are among the quietest large SUVs. The GL550 has more tire noise than other GLs, and its exhaust note is prominent. Even the diesel model is quiet at cruise. Wind rush is particularly well controlled.

Controls

GL320 CDI	GL450	GL550	Class Average
6	6	6	5.9

Gauges are large and easy to read. Most controls are logically placed, but some have cryptic markings and the navigation system absorbs most audio functions, complicating their use. Gear shifting is via a short steering-column lever with a toggling action that takes some getting used to, but the design frees up lots of space in the center console area.

Details

GL320 CDI	GL450	GL550	Class Average
7	7	7	7.4

High-quality materials, including standard real-wood trim, give the cabin a premium feel, though leather upholstery is standard only on the GL550. Controls adjust with a weighted, precise feel.

Room/Comfort/Driver Seating (front)

GL320 CDI	GL450	GL550	Class Average
8	8	8	8.6

Headroom and legroom are ample, and the seats are supportive and generously sized. Some testers say the cabin doesn't feel notably spacious, however. Entry and exit are easy via large doors and a no-stress step-in height. Outward visibility is good, but larger mirrors would aid lane changing.

Room/Comfort (rear)

GL320 CDI	GL450	GL550	Class Average
7	7	7	7.1

Outboard passengers have ample headroom and legroom and good seat support. But a relatively narrow cabin and low-hanging ceiling vents limit the center position to occasional use. Smaller adults fit in the third row, but only kids will be happy there on a long trip. Only the right-side section of 2nd-row bench seat slides forward for 3rd-row access, though it does create a large passageway.

Cargo Room

GL320 CDI	GL450	GL550	Class Average
9	9	9	8.5

Just a few grocery bags fit behind the 3rd row. A low floor height and 2nd- and 3rd-row seatbacks that fold flush with the deck ease loading and unloading. Relatively tight dimensions limit overall volume, however, and the rounded hatch opening limits cargo-item size. Numerous cabin storage areas, but none are generously sized.

Value within Class

GL320 CDI	GL450	GL550	Class Average
7	7	7	5.2

The GL-Class doesn't have the sheer interior volume of some premium large SUVs, but accommodations are more than adequate for the majority of buyers, and relatively trim exterior dimensions ease parking and maneuverability. Impressive power, high levels of refinement, and availability of a relatively frugal diesel model seal this SUV's Recommended status.

Total Score

GL320 CDI	GL450	GL550	Class Average
73	73	71	68.3

Scores for all Premium Large Sport-utility Vehicles

Low Score		55
Average Score		68
High Score		80