Can petroleum jelly help a burn?

If the burn isn't too serious, yes. It can also help with minor chemical burns.

ANS2:Do not use petrolatum on broken skin. It holds moisture and encourages bacterial growth. Use petrolatum only sparingly on sunburns and other burns that cause redness and irritation (first degree burns) only to keep the skin flexible or to reduce chafing. Read what the Mayo Clinic says about first aid for burns at the link below.