A couple of years ago I bought a new Mercedes suv and had it serviced by the dealership. After I brought it home I got a call from the service manager telling me that the guy that had worked on it wasn’t sure if he had changed the air filter. He asked me if I could bring it right back so that they could check. Since it’s a hour round trip I said I don’t think so. He then asked if he could have a tech come to my house that evening and check.
When the tech showed up he was very reluctant to have me come out into the driveway and see what he was doing. It was raining but I went anyway. He immediately reached into the engine compartment and pulled out a shop towel. He then checked the filter and even though it was new he changed it. While he was doing that I looked down and spotted a water bottle. He finally came clean and told me the truth. The air filter was only a ruse to get him under the hood so that I wouldn’t know that the guy that serviced my car had left a couple of things behind.