1- I just wanted to know what are the advantages and disadvantages of this kind of plugs. I have installed it in my Baleno JXR 2004 model with 140k kms, hiccups are gone and the car is smooth. But later on somebody told me that it increases fuel consumption and are not reliable plugs. They tend to leak more and as compared to other plugs. I dont know if this is psychic or what but my car is giving very less mileage for like 230kms in 30 ltrs :-/ . And if this is not the best plug for my car then also recommend me some good plugs.
2- If low mileage is not the problem with the plugs then what should I do?
Thanks!