Do I need any fasteners or adhesive to install this?

The wrap itself doesn't require adhesive — you overlap and tuck the end as you spiral it around the plug wire or line. Some users add a small zip tie at the overlap point for security, but that's optional depending on vibration and underhood movement.

Will this wrap damage my plug wires if they're already brittle?

If your wires are already cracked or splitting, wrapping them won't restore them. This wrap prevents future heat damage to good wires. Inspect wires before installation — if they're compromised, replace them first.

Can I use this on fuel lines or just ignition components?

Yes, you can wrap fuel lines and other heat-sensitive rubber hoses with it. Just keep it away from direct contact with fuel filler necks or any pressurized fuel connections where heat reflection might cause issues. Test fit and use your judgment on sensitive areas.