Some are.
Costco has an entire web page for car rentals for members. I have used it several times and it even worked when rentals were hard to find.
Not that I know
I don't believe so. You have to be a member. Having a car rental or someone that travels won't get a discount.
Many companies in both industries cater to Costco members with discounts and preferences. Costco itself doesn't have car rental company.
Yes they are.
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