2018 Mercedes-Benz GLS

2018 is a carry-over year of the X166 second generation (facelifted and renamed GLS for 2017). The volume GLS 450's 3.0L twin-turbo V6 makes 362 hp.

The GLS 450's twin-turbo V6 makes 369 lb-ft. It has no mild-hybrid assist; EQ Boost arrived only with the 2020 X167.

KBB and CarGurus both list 6.5 s for the 2018 GLS 450, and Mercedes' own claim was about 6.2 s. That is adequate but unremarkable for a roughly 5,400 lb three-row luxury SUV.

The twin-turbo V6 is smooth and quiet with modest turbo lag, but stop-start is somewhat abrupt. Rival X7-era and Range Rover engines are generally rated more refined, and the V8 GLS 550 feels more effortless.

The 9G-Tronic 9-speed automatic shifts smoothly in normal driving but can be slow to kick down and sometimes hesitates from a stop. The AMG GLS 63 keeps the older 7-speed.

Mercedes rated the X166 GL/GLS to 7,500 lbs with the factory hitch, which is near the top for unibody luxury SUVs. Body-on-frame Navigator and Escalade tow more.

4MATIC full-time AWD is standard on every 2018 GLS. The optional ON&OFFROAD/Off-Road Engineering package adds a two-speed transfer case with low range and a locking center differential.

AIRMATIC air suspension can raise ride height for real clearance, and low range is optional. It remains a road-biased luxury SUV with no axle lockers and no dedicated off-road trim.

There are three gas engines (V6, V8 and AMG V8), with no hybrid, PHEV or diesel in the 2018 US lineup. That covers a wide output range but offers no electrification.

The twin-turbo V6 GLS 450 is EPA-rated at 19 MPG combined for 2018, one MPG better than its 2019 rating.

The volume trim's EPA city rating is 17 MPG.

The volume trim's EPA highway rating is 22 MPG.

EPA publishes no range for gas vehicles, so this is derived from the EPA combined 19 MPG × the X166's 26.4-gallon tank. The large tank offsets the low economy.

EPA's annual fuel cost estimate for the 2018 GLS 450 is very high, driven by 19 MPG combined and the premium-fuel requirement.

Every 2018 GLS requires premium unleaded, and there is no regular-fuel, flex-fuel or diesel option in the US.

NHTSA lists the 2018 GLS-Class SUV 4WD, but every rating (overall, frontal, side, rollover) reads 'Not Rated', so under the framework the value is 0 (never rated). NHTSA never crash-tested the X166 generation.

IIHS never crash-tested the X166 GL/GLS, so the 2018 model has no award and no individual crashworthiness results. The GLS is a 2013-era design (facelifted and renamed for 2017) that predates the passenger-side small-overlap test, so it gets no benefit of the doubt beyond the absence of known structural concerns.

The volume 2018 GLS 450 comes standard with radar-based COLLISION PREVENTION ASSIST PLUS (forward collision warning with autonomous braking), ATTENTION ASSIST, Crosswind Assist and a rearview camera. Blind Spot Assist is optional on the 450 (standard on the GLS 550). DISTRONIC PLUS adaptive cruise, lane keeping and cross-traffic functions come only in the optional Driver Assistance Package, which is thin standard content for a luxury flagship.

IIHS published no front crash prevention result for the GLS. Standard COLLISION PREVENTION ASSIST PLUS provides radar-based autonomous braking for vehicles, but pedestrian detection and the PRE-SAFE PLUS/BAS PLUS functions require the optional Driver Assistance Package. This older-generation hardware has no published night or pedestrian test results.

Blind Spot Assist is optional on the volume GLS 450 and standard on the GLS 550. Active Blind Spot Assist, which brakes one side to stop a lane change, and BAS PLUS with Cross-Traffic Assist come only in the optional Driver Assistance Package.

NHTSA lists lane departure warning as optional on the 2018 GLS. Active Lane Keeping Assist and DISTRONIC PLUS Steering Assist come only in the Driver Assistance Package. When fitted, Steering Assist works on clearly marked highways but is less refined and needs more hands-on input than the later MBUX-era Active Steering Assist.

The optional DISTRONIC PLUS works across the full speed range, including stop-and-go, and adds Steering Assist. It is the previous-generation system, without the route-based speed adaptation of the 2020 X167. Because it is not standard, a base GLS 450 can be bought without adaptive cruise.

The 2018 GLS offers no hands-free highway driving: DISTRONIC PLUS Steering Assist requires hands on the wheel and times out quickly. Mercedes never offered a hands-free system on the X166.

The 2018 GLS has LED headlamps with the Intelligent Light System and Adaptive Highbeam Assist. IIHS never rated the X166 headlights, so with no published result the score stays below the Good-rated band.

The tall, upright greenhouse and commanding seating position give good forward and side sightlines. Thick rear pillars and third-row headrests create rear blind zones. Only a rearview camera is standard; the 360-degree camera that compensates comes in an optional package.

The second-row outboard seats have LATCH lower anchors and the third row has top tethers. The large rear doors and wide second-row bench make car-seat installation reasonably easy, though the anchors sit somewhat deep in the seat bight. IIHS never published a LATCH rating for the X166.

2018 is a carry-over year of the facelifted X166 second generation (2013–2019, renamed GLS for 2017). Every trim seats seven with a power-folding third row.

Front headroom is generous, typical of the tall, boxy X166 body.

The quoted front legroom is short for a full-size SUV, although reviewers do not flag the front seats as cramped.

The second row has ample headroom, and even the third row is close to 39 in.

Second-row legroom is competitive but not class-leading next to body-on-frame rivals such as the Escalade ESV.

The X166 has one of the more usable third rows among European luxury three-row SUVs: 35 in of legroom, 38.9 in of headroom and power-folding seats. Tall adults are still squeezed on long trips, and getting in requires tipping the second row forward.

There is respectable space behind the second row and usable space behind the third (16 cu ft), but it trails body-on-frame rivals like the Escalade and Navigator.

A maximum hold of nearly 94 cu ft is large for a unibody luxury SUV.

Everyday bins and console storage are conventional. The standard power-folding third row and power liftgate help, but there is no standout storage innovation.

The front seats are supportive and power-adjustable, and the optional multicontour seats are excellent. The second row is comfortable. The third row has adequate cushion height but is not adult-friendly for long hauls.

Standard AIRMATIC self-leveling air suspension gives a cushy, composed highway ride. Adaptive damping is better on the GLS 550, and large optional wheels add some impact harshness.

The cabin is quiet at highway speed with little wind noise. It hushes tire roar a step less well than the later X167 and the Range Rover.

Heated front seats are standard. Ventilated or massaging seats, heated rear seats and a heated steering wheel come in packages, and multi-zone climate covers the rear.

2018 is a carry-over year of the facelifted X166 GLS. The entry GLS 450 4MATIC listed at $69,550 plus $995 destination, which is above the $65,000 SUV band ceiling.

The GLS 450 was the volume trim. Dealer-stock units commonly carried the Premium and Driver Assistance packages plus metallic paint, which added roughly $5–7k to the $70,545 base.

CarEdge puts GLS 450 maintenance near $5,000 over five years, and KBB-attributed maintenance-plus-repair estimates for the GLS run near $8,700. The X166 has AIRMATIC air suspension, with known air-strut and compressor repair exposure, and comes with no complimentary scheduled maintenance, so the estimate sits at the top of the range.

KBB ranks the 2018 GLS in the 75–100th percentile for depreciation among 2018 SUVs, meaning it loses value faster than most. CarEdge puts typical GLS 450 retention near 49%, and the X166 sat below that.

Mercedes-Benz's New Vehicle Limited Warranty runs 4 years or 50,000 miles. That is par for German luxury brands and behind Lincoln and Cadillac's powertrain terms.

Mercedes-Benz offers no separate, longer powertrain warranty. The drivetrain is covered only by the 4-year/50,000-mile basic warranty, which is below the 5-year band floor.

The 2018 GLS includes no complimentary scheduled maintenance; prepaid plans are sold separately. Perks are 24/7 Roadside Assistance for the warranty term and an mbrace connected-services trial, which is thin for a $70k+ SUV. The 2018 BMW X5 had free scheduled maintenance (BMW Ultimate Care) for 3 years/36,000 miles.

$76,000 volume-trim price minus its estimated resale value after 5 years (44% retained, or about $33,440) leaves about $42,560 in depreciation. Add the projected $9,500 in 5-year maintenance and repairs, and owning this vehicle for 5 years costs about $52,060 in total.

MY2018 is the third year of the facelifted X166 GLS, a platform launched for 2013, so its early faults had mostly been worked out. The sources disagree. RepairPal rates the GLS450 above average and owners give it high marks, but Car Guide scores its reliability poorly, and AIRMATIC air-suspension failures are the problem cited most often. Taken together that is average for the segment.

Mercedes-Benz places mid-pack to lower-mid in both J.D. Power's Vehicle Dependability Study and Consumer Reports' brand rankings. It ranks ahead of Land Rover, but behind Lexus and usually BMW.

Four NHTSA campaigns cover MY2018, which is typical and well below the 2020 X167's count. Two are fleet-wide eCall software fixes. One recalled about 9,000 GLE/GLS units because rear brake caliper pistons were not coated correctly, which can reduce braking; the remedy is a brake bleed. The fourth, a door-lock indicator fault, covers only the 2018 GLS550, not the volume GLS450. There are no powertrain or fire campaigns.

The volume GLS 450 4MATIC uses the M276 3.0L biturbo V6 (362 hp) with the 9G-Tronic 9-speed automatic. Both are high-volume units used across the Mercedes lineup, and MY2018 has no powertrain recalls. Earlier M276 builds had camshaft-adjuster and timing-chain complaints, and oil leaks are common as the engine ages, which leaves it a mixed rather than proven-bulletproof family.

The X166 cabin uses wood, leather and soft-touch surfaces throughout and is solidly assembled. Its COMAND screen and button-heavy console were already looking dated against the redesigned 2018 Lincoln Navigator. It is rich for the class, just not class-leading.

As a sixth-year platform built at MBUSI in Tuscaloosa, the 2018 GLS is generally well assembled, and owners report only scattered rattles. The caliper-coating recall is a supplier and process quality escape, but it is not a body or trim fit problem.

Mercedes-Benz has one of the densest luxury dealer networks in the US, with roughly 380 dealers and mature service operations. Its service-satisfaction results are competitive within the luxury segment.

Parts are plentiful, and the high-volume M276/9G-Tronic powertrain has decent aftermarket support. Mercedes repair costs are still well above average: AIRMATIC struts and compressors, ADS dampers and COMAND electronics are costly fixes, and every 2018 GLS is long past its 4-year/50,000-mile warranty.

The 2018 X166 GLS uses a non-touch 8-inch COMAND display driven by a console controller and touchpad. MBUX dual 12.3-inch screens arrived only with the X167 for 2020.

The pre-MBUX COMAND interface is dated against its peers: the touchpad and rotary combination and deep menus are clunky, and there is no touch input or natural-language voice.

For 2018, wired Apple CarPlay and Android Auto were optional, through the $350 Smartphone Integration package or the Premium Package, not standard. Wireless projection was never offered on the X166.

On the GLS 450, COMAND navigation with map updates is part of the Premium Package. Voice control is command-based: functional but rudimentary.

The base audio is decent. harman/kardon LOGIC7 surround is available, with Bang & Olufsen BeoSound at the top of the range.

The cluster is analog gauges flanking a small center multifunction display. A full-digital cluster came only with the X167.

There is no meaningful over-the-air update capability. Map updates come through the Premium Package's map-update service.

The mbrace / Mercedes me app covers remote lock, locate, vehicle status and remote start. It is subscription-based, and there is no digital key.

Power is USB-A and 12V outlets only, with no USB-C. Wireless charging was not offered on the 2018 X166.

KEYLESS GO proximity entry and hands-free access come in the Premium Package on the GLS 450, and the power liftgate is standard. There is no phone-as-key.

A rearview camera is standard. Surround View and Active Parking Assist come in the optional Parking Assistance package.

No head-up display was offered on the X166 GLS. The X167 added one for 2020.

Seven seats, big rear doors and a power-folding third row make family duty easy. Cargo shrinks to 16 cu ft with all rows up, and the tall step-in is a stretch for small kids.

There are no NHTSA or IIHS crash tests for the 2018 GLS. Forward collision warning with braking is standard, but blind-spot and lane-keeping assist are optional on the GLS 450.

A quiet, cushy air-suspended ride and a usable third row make it a strong long-trip hauler. Rear amenities (rear climate, optional rear entertainment) are adequate, but luggage space with all seven seats filled is limited.

It is smooth and calm in traffic, but the 9-speed can hesitate from a stop and stop-start is less polished. Its sheer size takes concentration in town.

At 17/22/19 MPG on premium fuel, the V6 GLS 450 is expensive to commute in (EPA about $4,250/yr in fuel).

A long body on a 121-inch wheelbase and a 40.7 ft turning circle make it cumbersome in cities. Surround View camera help is optional, not standard.

A 7,500 lb tow rating, a twin-turbo V6 and a 94 cu ft maximum hold handle moderate towing and hauling. It is a luxury SUV, not a work tool.

It is luxury-oriented and not built for abuse. X166 AIRMATIC strut and compressor failures are a known expense under heavy use.

There is no onboard power, no bed and no work-focused features beyond a trailer hitch and roof rails.

It is a quiet, comfortable mile-eater with roughly 500 miles of range from the 26.4-gal tank. DISTRONIC PLUS with Steering Assist is an option, not standard.

Standard 4MATIC AWD, a raisable air suspension, a 7,500 lb tow rating and roof rails make it a capable all-weather tourer. The optional Off-Road Engineering Package adds low range.

The power-folding second and third rows fold flat to nearly 94 cu ft, and a tow hitch and roof rails add flexibility.

It is secure and stable but heavy and softly tuned. There is noticeable roll in the GLS 450, which lacks the active roll control of higher trims.

The electric power steering is precise enough but light and numb, typical of a large luxury SUV.

The brakes are adequate for a roughly 5,400 lb SUV, with a progressive pedal. No instrumented stopping data for the 2018 model was found.

The twin-turbo V6 is smooth with modest turbo lag. The 9-speed is sometimes slow to kick down, and stop-start can be abrupt.

The V6 is well isolated and unobtrusive under load. The GLS 550 V8 adds a pleasant, muted burble.

The turning circle is large, reflecting the 121.1-inch wheelbase.

The upright, commanding seating position gives good sightlines. The COMAND controller and column-mounted shifter take some adjustment, and some controls are scattered.

The GLS 450 is pleasant but more serene transporter than engaging drive. The GLS 550 and AMG GLS 63 add real character.

The 2018 GLS 450 comes standard with 4MATIC, AIRMATIC air suspension, a power-folding third row, automatic emergency braking, crosswind assist and Pre-Safe. However, adaptive cruise and active lane control were in the optional Driver Assistance package, which is typical German option pricing.

At $70,545 delivered, the GLS 450 was priced in line with the Lincoln Navigator and below the Escalade, Land Cruiser and LX, with a usable third row, 7,500-lb towing and 362 hp. However, its cabin tech was aging and driver aids cost extra.

There are three well-spaced US trims, the V6 GLS 450 ($69,550), the V8 GLS 550 ($94,950) and the AMG GLS 63 ($125,300), plus a deep option list and the mid-2018 Grand Edition. All are 4MATIC and gas-only, since the US diesel GL was dropped.

In 2018 the GLS was a steady US seller near the top of the three-row luxury segment, roughly 30,000 units a year. It faced no BMW X7 yet and outsold the Lexus LX and Infiniti QX80, though it trailed the Escalade.

The GLS is the flagship of Mercedes-Benz's SUV range, and Mercedes-Benz remains one of the strongest luxury brands. Steep depreciation shows the image does not fully carry into resale.

As a mid/late-cycle German luxury SUV in a normal pre-pandemic market, the 2018 GLS commonly drew lease support and dealer discounts below MSRP. There was about $4.9k between invoice and MSRP to negotiate with.

The X166 generation launched for 2013 and was facelifted as the GLS for 2017, so 2018 is a sixth-year carry-over. The redesigned X167 followed for 2020, and the 2018's older COMAND tech was soon superseded by the X167's MBUX.

Reviewers credited the GLS with a comfortable ride, a usable adult-capable third row and strong engines, but noted its dated interior tech. It won no major awards, NHTSA never crash-tested it, and IIHS had tested it only partially.