3500 4x4 Pickup V10-488 8.0L Magnum (1994)
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.