I was in Dusseldorf for 16 hours and had to drive about 110 kilometres to the Dutch border. I had ordered the smallest car and was given this DS3. I really liked it but had two complaints, one comment and one question?

Complaints. ... a small boot with literally a letter box type hole to get your stuff into. Very compromised and is swiftly followed by very poor rear vision when the roof is open.

Comment....I am sure that it had a three cylinder engine. A slight thrum made it feel so, but not all the time. It was geared to about 20mph/1000rpm which is very low these days, but even at 80mph the car was not noisy. I like the thruminess!

Questions....there is a clear plastic knob at the top of the dash. Could not work out what it did. No instructions in the car.

Can anyone help?