Too bad they didn't check it the first time!
I recently brought my Silverado in for service. While the service I received was adequate, I was disturbed to find that a problem I brought my truck in for 5 years ago was finally addressed. After owning my truck for less than a month, I brought it in because I had very little airflow from my vents when using the heat. This was in January, so the temp outside was predictably cold. I was assured that there was nothing wrong with my heating unit. When the problem continued, I once again requested that the issue be checked, as my air conditioning unit didn't keep up, either. Finally, after owning my truck for 59 month, the tech checked my air filter and it was plugged! Every time I have brought my vehicle in for service the boxes are marked off that my air filter was checked and found satisfactory. Thankfully, I now have a working heater. Unfortunately, I don't feel I can trust that the service department has done what they "say" they have done after "checking" my air filter multiple times a year when it was just done for the first time in all the visits I have made to the dealership.