X166
GL/GLS-Class
Overview
The X166 continued as the GL-Class before being renamed GLS-Class in 2017 as part of Mercedes' global naming strategy. It refined the full-size luxury SUV formula with improved materials, more powerful and efficient engines, and enhanced driver assistance systems. The GLS63 AMG with the M157 5.5L biturbo V8 producing 577 hp was effectively a high-performance luxury bus capable of sub-5-second 0-60 times with seven passengers.
Engines & Transmissions
Engine Options
- M276 3.0L V6 Biturbo (GL/GLS400)
- M278 4.7L V8 Biturbo (GL/GLS550)
- M157 5.5L V8 Biturbo (GL/GLS63 AMG)
- OM642 3.0L CDI V6 (GL/GLS350d)
Transmissions
- 722.9 7G-Tronic Plus
- 9G-Tronic (725.0, GLS facelift)
Common Problems
Known issues reported across the X166 production run, ordered by severity. These are based on our direct experience servicing these vehicles over 35 years.
Airmatic compressor failure and front strut air spring leaks
High severityM278 V8 timing chain cover gasket oil seepage
Medium severityThird-row seat folding mechanism motor failure
Low severityTransfer case seal and output shaft bearing wear
Medium severityDEF (AdBlue) system heater element failure causing dashboard warning
Medium severityMaintenance Highlights
Key service intervals for the X166. These are based on our recommended schedule for Southern California driving conditions, which may differ from factory-specified intervals.
Reliability Assessment
Based on 35 years of service data at Beach Benz
Beach Benz Experience
“The X166 GLS is a well-built full-size luxury SUV. The V8 biturbo models need proactive timing chain cover gasket monitoring, but otherwise they are very reliable. We see many of these as family haulers in Orange County and they hold up well to daily use.”
— Beach Benz service team · 35+ years of Mercedes-Benz specialization
Your X166 deserves a specialist.
Factory diagnostics. OEM parts. 35 years of Mercedes-Benz expertise. Whether it's a routine service or a complex repair, Beach Benz has your X166 GL/GLS-Class covered.