Yes, the study does recommend 10 " H2O above the clean filter restriction as a "rule of thumb" air filter change point, but on a factory installed gauge I believe that the manufacturer selects the red zone as the normal filter replacement point. In any case, if the drop in power is objectionable just change the filter earlier at 50% for example. In most situations, if you are not often driving on dirt roads, the air filter will last far longer than you expect. Installing these filter minder gauges is one of the best things that General Motors has done on its trucks. This saves the owners money on filters and extends engine life. A rare win-win situation.