Is interest received on loans given to a friend for purchasing a car included/excluded in national income?

No,

The interest received on loans given to a friend for purchasing a car will not be included in the national income because it is a non-factor receipt as the loan is not used for production but for consumption.

Explanation:-

Interest received on loans taken for consumption purposes does not add to the current flow of goods and services.

Thus it will not be added to the national income.