Fuel quality in the United States has been a major challenge for Common Rail Diesel owners. Water contamination and poor maintenance adds to the problems. With the advent of Common Rail, gone are the days when a Diesel engine would run on poor quality fuels. Wear has increased significantly as injection pressures have increased and fuel lubricity has declined. We always recommend you try a fuel system cleaner designed for Common Rail systems before replacing injectors or sending them to us for evaluation. F1 likes the Stanadyne Common Rail injector cleaner available at most Autozone stores.