There's filters they sell to install in the CP4, but they're not guaranteed to stop the contamination from getting to the injectors. CP3's wear out, but rarely do you ever hear of one grenading unless it's tuned and pumping the rail pressure up, or large amounts of contaminated fuel runs through one. For GM, only the LML has a CP4(11-17), they switched to DENSO fuel systems for the L5P after all the CP4 failures, and Bosch's response. Should be interesting for Dodge since Cummins just switched to the CP4 to meet emissions, and Ford is sticking with them. The CP4 runs on the ragged edge since the pistons in it are moving twice as fast as a CP3. Any air, water, or even a minuscule amount of gas will DESTROY a CP4 in a matter of a few miles. Ford uses an air sperating double fuel filter system which is why I think you see slightly fewer CP4 failures on the Ford's, but there's fail as well. If it was me, I wouldn't buy a new diesel unless I had to have the extra torque to tow. Emissions have just about killed the reliability, and the repair cost's have gotten out of hand to say the least.