According to the price list of the W213 E-Class for the German market from mid-2018, Mercedes-Benz dropped the V6 petrol M276 and V6 diesel OM642 from the middle-class sedan lineup. The newcomers are the R6 M256 and OM656, currently offered under the name AMG E53 4MATIC+ and E400d respectively. This marks the end of the V6 E-Class in the European market, although some oversea areas will receive the old V6 M276 for a longer time.
See the E-Class lineup in Germany here:
The late 1990s was the era of eliminating R6, which is considered too large to fit in FF chassis and thus not able to reach economies of scale by sharing engines between FF and FR chassis. In contrast, a V6 can be placed both longitudinally and transversely, so TOYOTA and NISSAN halted the production of the R6 and share the V6 between economical and luxury models e.g. TOYOTA Camry 3.5 and LEXUS GS350. Entering the 21st century, the only prominent carmaker offering R6 engines is BMW.
I would say that the V6 story of Mercedes comes with blood and tears. The German luxury carmaker debuted its first passenger V6 engine, M112, in 1997. It was somehow believed that the move was a preparation for the merger of Daimler-Benz and Chrysler, which were expected to form the super-group in the auto industry with comprehensive coverage of the market. However, as everyone knows, Daimler-Chrysler turned out to be a tremendous business tragedy.
Although some Mercedes and Chrysler models did share the V6 engines, the sharing between the two was not enough to make profits. After the sale of Chrysler in 2007, Mercedes continued to offer V6 in upper-class models (excluding A-Class chassis). During the approximate 20-year history of the V6, Mercedes produced the petrol M112, M272, M276, and the diesel OM642, with displacements ranging from 2.4 to 3.7 liters. The latest models are the 3.0L turbocharged petrol M276 and 3.0L turbocharged diesel OM642. Starting from late 2017, the new R6s M256 and OM656 reach the market, first in W/V222 S-Class LCI.
The last badges of Mercedes’ V6 before the R6 takes its place are 400, AMG 43 for petrol, and 350d for diesel. Overall, both petrol and diesel are 3.0L worldwide. In 2014, Mercedes switched from the 3.0L turbo petrol to the 3.5L turbo petrol in W212 E-Class and C218 CLS-Class in certain markets without public announcement, though the USA and most Asian markets still got a 3.0L E400 and CLS400. The 3.0L E400 and the 3.5L E400 have almost identical specs, except that 3.5L has lower turbo pressure and lower carbon emission. When the E-Class entered the W213 generation, the 3.5L was carried over from W212 in the beginning. Therefore, some markets received E400 with 3.5L, and AMG E43 with 3.0L. It is still unclear why Mercedes did that.
Unlike V6, R6 is an inherently balanced structure. That is why heavy-duty engines and industrial combustion engines are mostly in R6 or V12. The only major problem with R6 is its size. The size of the R6 has not been drastically reduced over the past 10 years, but under the trend of downsizing, carmakers no longer consider a 6-cylinder FF layout. This is probably why R6 revives in the luxury range.
If you really want a V6 Mercedes, it is still possible to buy one in the USA, for example. They currently receive 3.0L M276 under badge 450.
Update: in Oct. 2018, the E450 4MATIC with M276 was added to the German market lineup. Seems that Mercedes decided to keep offering M276 longer.
