@UK
Hamilton can use his joker engine rule in the next gp only because as the rule stated on formula1.com is
"Joker Engine Rule:
From 2008, a driver will not be penalised the first time he needs a replacement engine during the season, unless it is at the final event of the championship.
So now you can see that Hamilton has only one race left for using the rule and as he already on his way to get a new engine in the next race he needs a good reason for joker engine in the last race and even if he gets a joker engine he will be penalised for may be 5 or a 10 grid penalty and on Interlagos having a grid penalty means chaos is around the first corner.