MB put a lot of effort into the 126, and it is quite different in a myriad of ways.

The 126 was designed with a strong nose toward improving safety and aerodynamics (for better performance and fuel economy) over the brick-like 116, while maintaining the basic exterior look of the 116. This was not an easy task and a testament to Bruno Sacco and his design team.

Early pre- and production 126s from around 1978-79 showed a 14% improvement in Cd over the 116, to 0.36. At this time, this was the lowest Cd available in a production car. ANY production car.

Weight reduction was also a strong consideration. This was achieved in a number of ways, including the use of all-alloy engines and lighter materials. The weight difference between the top-of-the-line 116 (the 450SEL 6.9) and the early top-of-the-line 126 (the 500SEL) was well over 600 lbs!

The 126 body is nearly 2 inches narrower than the 116's, but there was no sacrifice in interior room, and actually an increase in room as measured from front to rear.

Increased safety was a HUGE point of difference between the two cars. The 126 had an entirely new, redesigned front crumple zone and new A-pillars with improved strength. The doors of the 126 were attached in a new way that reduced the likelihood that they would be unopenable in the event of a crash. Stronger steel plating in the frame increased overall chassis strength, but weight less than the 116's. Bumpers were aluminum rather than the steel of the 116.

Road and wind noise were significantly reduced by the application of rubber more intelligently, in the rear suspension subframe, and around "wind catch" points such as the door frames and other body seams. A double bulkhead was employed (first time MB used this design) under the hood to isolate the engine from the passenger compartment noise-wise (aluminum engines are perceptibly noisier than iron-block engines).

Interior changes: larger door openings; reshaped seats (electrically adjusted for all seats -- electric adjustment was only available in the 116 as a Euro-only option and only for the 116 rear seat); more front legroom due to a front seat redesign.

New HVAC (ACC) system. Adjustable top seatbelt anchors. Airbag for mid- to late-models. ABS (only available in 1979 model 116s, as an expensive option and only in Europe). Redesigned steering wheel (smaller by 1 cm, and with a slightly dished shape on non-airbag cars) and redesigned steering linkage for better safety in the event of a collapse.

The 5.0L engine weighed 114 lbs less than the 6.9 engine; the 3.8L engine weighed 295 lbs less than the outgoing 4.5.

A new four-speed torque-converter transmission was used in the 126, which improved fuel economy and smoothness over the previous torque-converter automatics as used in the 116 chassis.

Rustproofing on the 126 was light-years ahead of the 116's.

Hope this helps.

Cheers,
Gerry