My bad ,
Should of researched a bit more before posting .I'm guessing your M5 isn't diesel.
. Below is copied and pasted from car magazine :-
A recall in October last year identified 268,000 diesel BMWs in the UK requiring potential remedial work, with 1.6 million vehicles affected worldwide. The fault concerns a possible glycol leak in exhaust gas recirculation (EGR) valve coolers, which could lead to fire “in extreme cases”.
Complaints range from long waits with poor communication and unsuitable hire cars, while some readers told us they had not been sent recall letters, only finding out their cars required the work when they were in dealerships for routine servicing.
Which models are affected?
Examples of the 3 Series, 4 Series, 5 Series and 6 Series, X3, X4, X5 and X6 with four-cylinder diesel engines produced from December 2014 August 2016, and with six-cylinder diesel engines made from July 2012 to June 2015.
Examples of the 1 Series, 2 Series, and 7 Series, and X1 with four-cylinder diesel engines made from March 2011 to January 2017, and with six-cylinder diesel engines made from August 2010 to June 2015.
What is an EGR valve?
Exhaust gas recirculation valves reduce harmful NOx emissions by recycling a portion of exhaust gases into the combustion chamber, reducing the high ignition temperatures associated with NOx production. EGR valves run hot and require cooling; in affected diesel BMWs, EGR coolers that can leak, posing a potential fire risk.