I 1+ pistonhead !
its been years for me too, never had any issue with sludge ! use good oils on time service, never had such issue,
using super running in all these cars from past many years ! no problem so far !
baleno 1999, 140k +
gli 2007, 80k +
gli 2010, 25K+
city 2006, 55k+
i have to agree on one thing with hasnain that sometimes if i filled from some bad filling station, the petrol octane rating screw car's detonation, gives knocking, so have to finish that fuel and fill from my regular filling station and all is well