The Mercedes-Benz W126 S-Class, which debuted in 1979, cemented Mercedes-Benz’s status as a premier luxury car manufacturer, building upon the safety and engineering foundation laid by the earlier W116. Throughout the 1980s, the W126 became synonymous with success and high-end automotive engineering. Within this prestigious lineage, the 1990 Mercedes 420sel stands out as a significant model, embodying the pinnacle of late-era W126 refinement and luxury for the discerning driver.
The design of the W126 S-Class marked a shift towards improved aerodynamics and greater fuel efficiency. Compared to its predecessor, the W126 boasted a 14 percent reduction in drag and a relatively lighter weight, starting around 3,600 pounds. This focus on efficiency, particularly in six-cylinder and diesel variants, was notable for its time, especially when measured against the large American sedans of the era. Safety was also paramount, with features like a driver’s side airbag available for most of its production run, and a passenger airbag becoming standard in 1990 Mercedes 420SEL models and beyond. The introduction of traction control and seatbelt pretensioners further underscored Mercedes-Benz’s commitment to occupant safety.
For the American market, the W126 S-Class can be broadly categorized into two periods: 1979-1985 and 1986-1991. Initially, the U.S. received the 380SE/SEL and 500SEL models, both equipped with V8 engines. However, a significant mid-cycle refresh in 1986 brought about models like the 300SE/SEL (inline-six), the 1990 Mercedes 420SEL, and the top-of-the-line 560SEL (V8). The coupe versions, known as SEC models, were available as 380 and 500 initially, and later as 420 and 560 after the update. Notably, the earlier 380 models, and to some extent even the early 420s, were perceived as somewhat underpowered due to emissions regulations. By 1986, the 300 models offered performance comparable to the U.S.-spec 420.
Diesel engines also played a crucial role in the W126 lineup. From 1980 to 1985, the U.S. market saw the five-cylinder 300SD, followed by the six-cylinder 300SDL in 1986 and 1987. Continuing the diesel legacy, the 350SD and 350SDL models were introduced in 1990 and 1991.
The mid-cycle update that refined the 1990 Mercedes 420SEL also brought visual and interior enhancements. These later W126 models are identifiable by their flush-face halogen headlamps and integrated headlight wipers. Inside, improvements included electronic automatic climate control, an electrically adjustable steering column, and leather trim on the steering wheel and shift lever. Heated front seats were standard in the 560SEL and 560SEC, and optional across the rest of the range, including the 1990 Mercedes 420SEL. A luxurious two-place rear seating option, featuring power-adjustable seats and a burl-walnut center console, became available for the 500SEL and 560SEL models, accompanied by plush Arametta suede-like leather upholstery.
In terms of mechanical robustness, the powertrains of Mercedes W126 models are renowned for their durability, often exceeding 200,000 miles with proper maintenance. Engines frequently outlast transmissions. However, components like front-end and steering bushings will likely require replacement sooner. While general repairs are not excessively complex compared to other European cars of the period, parts costs can contribute to a higher overall ownership expense for a 1990 Mercedes 420SEL. Vacuum-operated power locks can be a source of intermittent issues, and the climate control system, while advanced for its time, is less effective than modern systems and can be costly to repair.
Diesel engines, generally, are known for even greater longevity than their gasoline counterparts, although fuel system issues can arise in colder climates or with infrequent use. It’s worth noting that the 350SD and SDL models have not garnered the same reputation for reliability as other W126 diesels due to potential issues with bent connecting rods and cracked cylinder heads in certain production years. For any of the later diesel models, including some contemporary to the 1990 Mercedes 420SEL gasoline versions, replacing engine mounts is essential. For 1986 and 1987 300SD models sold in California, the original particulate filter should have been replaced with an oxidation catalyst if it hasn’t been already.
The W126 S-Class gained notoriety as a popular model for gray-market importation into the U.S. in the mid to late 1980s. Models like the 500SE and 500SEL, considered top-tier in the lineup from 1985 to 1991, were not officially sold in the U.S. with their full European specifications. This limitation in features and finishes led dealerships to import approximately 22,000 of these vehicles outside the official U.S. sales network. While the 1990 Mercedes 420SEL was officially available in the US market, this gray market phenomenon underscores the strong desirability of the W126 and its variations.
The 1990 Mercedes 420SEL represents a high point in the W126 S-Class story. It offers a compelling blend of classic Mercedes-Benz luxury, robust engineering, and enhanced features from the model’s later production years. For those seeking a distinguished and reliable classic luxury sedan, the 1990 Mercedes 420SEL remains a compelling choice, offering a taste of 1990s flagship motoring with enduring appeal.
