Can a 15 yr old grandchild with a learners permit who does not live with you drive your car if you are with him without being added to your insurance?

A minor with a learner's permit can only drive with an adult in the vehicle. It can be any adult with a valid driver's license. The minor does not need to be added on to the policy until they have a valid driver's license.

The adult must also be of a certain age, not just 18. Different states might have different age restrictions.