CDW and SLI are both offered by the rental car company for a daily fee.

The insurance offered by AMEX is secondary insurance, meaning it falls upon your primary insurance to handle the claim first and then whatever is left, AMEX will take over.

Theoretically if you dont have personal insurance then the AMEX becomes primary and you should be covered, theoretically.

But if you have an AMEX and purchase the "Premium Rental Car Insurance" then the coverage is primary, which means regardless of if you have personal insurance or not your rental is covered by AMEX and you never have to touch your personal insurance.

Again, this is a form of CDW only, not SLI.
https://www295.americanexpress.com/p...do?source=CCSG

When I rent a car, I...
- make sure I have enabled "Premium Rental Car Insurance" on my AMEX.
- Rent with that AMEX.
- Decline the expensive CDW offered by the rental company.
- But I do purchase the SLI from the rental car company.

This definitely makes sure that if I travel and, god forbid, get into an accident with someone else, I never have to touch my personal insurance.