Common Misdiagnosis in Warranty Repair
There are many reasons why a dealership or repair facility may deny warranty coverage on a repair. Sometimes, people make mistakes, and technicians are no different than anyone else. A less common reason is the few "bad apples" out there who try to charge a consumer for a legitimate warranty repair, so they can make a greater profit. You don't have to be a master mechanic to challenge a repair diagnosis, just an educated consumer. In all of these cases, you should contact K&N's Service Provider Support group at 800-858-3333. Here are some preliminary resources that might be helpful.
Problems related to the use of an "aftermarket oiled air filter"
Maybe you've seen this phrase on your repair order. The dealership or repair shop says that certain engine parts or sensors need to be replaced because you have been using a K&N air filter. The truth is that oil does not come off our air filters, even under extreme conditions. The amount of oil applied to our air filters is small (usually less than 2 ounces) and once that oil is applied and evenly absorbed it will not come off until the filter is cleaned. We conducted a test with an over-oiled K&N air filter in which we flowed 1,000 cubic feet of air per minute through the filter for over twelve hours. The use of an absolute filter downstream revealed that no oil came off the K&N air filter, even in these extreme conditions. Many companies, both aftermarket and OE, use oil in their air filters, both disposable (paper) and reusable (cotton). We all use oil for the same reason: it enhances the filtration efficiency of an air filter.
Mass Airflow Sensors
The dealership or repair shop says that your vehicle's mass airflow sensor needs to be replaced, and is blaming it on the K&N air filter you installed. What steps did the technician take to arrive at that conclusion? We have never encountered a dealership or repair facility that owned the equipment necessary to test whether or not a sensor was functioning properly or to measure its output. Certain vehicle manufacturers have issued bulletins on how to test a mass airflow sensor by installing it into a "similar vehicle", but in our experience those instructions are rarely followed. There are two common types of mass airflow sensor failure: failure from silicone contamination of the sensing element, and complete electronic failure. Both of these types of failures can only be verified through microscopic, forensic/chemical, and airflow/sensor output analysis. More on Mass Airflow Sensors here.
The dealership or repair shop says that your K&N filter let too much dirt pass through, causing premature engine wear and "dusting" of your turbocharger or engine. Dust ingestion can be hard to verify without doing a complete teardown of the engine and performing a filtration efficiency test on the air filter. Performing an oil analysis on the engine oil used at the time of failure can uncover a dust ingestion problem. If a dust ingestion problem is found, it is most likely caused by an opening or defect in the air box or air inlet duct, a fuel filter that needs replacement, or engine oil beyond its service life. It is unlikely that an air filter is the cause.