My Astro van engine is Vortec, using 5 qts, just slight overfill. Big engine 6.2L Vortec engine uses 6 to7 quarts of oil, depend on 2WD or 4WD vehicles with or without auxiliary oil cooler.
Yes that is true many novices at the quick lube shops, make mistakes for overfilled or wrong grade. I believe the modern lube shops have the specs of the oil capacity, weight and grade when the service writers input the vehicle's year/ maker/ model and VIN then computer will print out the spec papers and hand over to the lube technicians to read the specs and instruments before begins lube works
