S Class tyre pressures

[MancMike]

204 blue efficiency is a thing.

Mark’s will be given it’s the 1.6T rather than the earlier 1.8k.

 

[markjay]

My car is BlueEfficiency - I believe that all Start/Stop cars are - but I think the main difference between my car and MancMike's is the heavier front on his car due to the larger engine.

Additionally, my car being the facelift model, will have weight reduction in various places and will also be lighter overall.

So probably my car is lighter and has more balanced weight distribution betweeb the front and rear axles, compared to MancMike's car..

 

[190]

The original C180 K BE model was fitted with 195/60 tyres to get CO2 down to 149 g/km. When the same car was fitted with 205/55 tyres it jumped up to the next VED tax band. If they went to that extreme chasing lower headline emissions then it's possible they might also have added a few extra PSI in the tyres.

For what it's worth I looked into the effect that tyre pressure has on rolling resistance and therefore MPG. It's s not straight forward because the impact of rolling resistance varies with speed but on average I concluded a 10% change in pressures has only 0.8% impact on MPG. There would be a law of diminishing returns in that the 1st 10% increase in pressure would gain 0.8 % mpg but a further 10% increase would not net as much improvement.