I had the oil of my '68 350 AT 2bbl Firebird chaned. That you can't trust the oil dipstick 100% due to the tube and its installation is known. The garage replaced the filter and filled in 6 qt - they used an AC Delco PF61. This filter doesn't have a capacity of 1qt. Is the PF61 ok? Is it really a problem if there is more oil filled in, say 1/2 qt?