Getting Mercedes to commit to a date for when we'll see the Diesotto unit in cars on sale in the UK is like trying to get a straight answer from a politician on Question Time.
Mercedes says three conditions have to be met to determine when the engine will be ready to go into production cars.
The first is that they have to work on the reliability of the engine and its components, the second is to make production of the engine cost-effective, and the third is to do with the management of the engine.
The concept car has four electronic control units to manage the complex processes inside the engine, and Mercedes wants to combine these units into one ECU.
However, last year, the company did say that we could see Diesotto engines within five years.
The S-Class will be the first car to get the ground-breaking engine, but Mercedes says it has built the unit so that it can be adapted for other cars in its stable - the E-Class for example - although not for smaller models such as the A- and B-Class.