Prado cracked pistons

In July 2011 near Kunanurra WA the engine in my 2006 Toyota Prado D-4D diesel suffered two cracked pistons. I had owned the vehicle for 4 and a 1/2 years, but it had only traveled 85,000 km, and had been log book serviced by a licensed mechanic I have known and trusted for years. I took it to the Toyota dealership in Kunanurra and picked it up in Perth five months later with a new motor. The cause of the engine failure I am told was due to injector failure caused by poor quality fuel. The repair bill was close to $30,000 with replacement motor and transport costs and testing of the fuel. My insurance company accepted the claim and paid for all but $1800 of the repair, plus airfares to and from WA, and $1400 caravan park rent. I have become aware that this problem has occurred to quite a number of these D-4D motors between 50,000 km and 100,000 km. My question is as to how best to care for the new motor and avoid a repeat of the above in what is a short distance, well short of Toyota's 100,000 km warranty claim. I asked Toyota what I should do, but got no response. A local Toyota dealer advised me to speak to a diesel expert. I did and was told that the fuel filter was the incorrect fuel one and would restrict the flow of fuel to the high- pressure pump and damage the motor. The Toyota dealer insisted the advice was incorrect when I returned to buy a spare. They also stated that the low standard of diesel fuel in Australia is the cause of the injector failure, which in turn causes the pistons to fail and the motor damage. If this is true, why does Toyota continue to sell this motor in Australia? This experience has shattered my confidence in the long-term reliability of this vehicle.