Faulty Injector

I am using VW vento highline. It was very good in 2 years,i.e. the warrenty period. but once the warrenty period is over,it started creating problem with the injector. Service centre says water in fuel, dust in fuel, kerosene in fuel. each six month I am changing the injector.
I had asked them whether I should use high speed, or pure diesel, i.e. turbojet or speed etc, but the service centre is saying nothing. They are just mum on this issue.

If dust and other is a problem then why this donot happen in Other diesel cars? why only in vento.

History of my car

Purchase Oct 2011

warrenty Sep 2013

First injector problem Nov 2013

Second injector problem Oct 2014

Third injector problem Oct 2015.

Just see in two years of warrenty, nothing happens, after 2 years all problem starts. This is actually fabricated I feel.

Please be careful in purchasing this car specially the diesel version. I cannot say about petrol version.

VW is not taking any steps to solve the issue.