Question about oil for high mileage cars

[greg@xxxxxxxxxxxxxx]

I've noticed Valvoline and I think Castrol both have special oils for
"higher mileage" vehicles. Anyone know if there is anything chemically
unique that justifies their claims of being better than regular oil?

I'm using Castrol 20w50 on my 74 Spider w/about 110k miles. This is their
regular oil,not the "special" oil.

Anyone have any experience or other information about the credibility of
these special oils or is it just as well sticking with regular oil.

Thanks,
Greg
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