Fillpipe Restrictor: Description and Operation
Fill Pipe Restrictor:
The fuel tank filler tube has a small diameter center opening to prevent the larger service station nozzle, used for leaded fuels, from being inserted into the filler tube, thereby preventing system contamination.
Since the use of leaded fuels contaminates the catalyst, deteriorating its effectiveness, the use of unleaded fuels is mandatory in all vehicles with catalytic converters.