Vince_vice is correct. Heat transfer is proportional to the temperature delta. In other words, the coffee cools fastest when the coffee is hottest. The rate of cooling slows as the coffee and outside approach the same temperature. So yes, it makes a difference when you add the cream.
N8Lux t1_iubsk25 wrote
Reply to comment by Vince_Vice in [OC] When should you add the milk in a cup of coffee? by Prunestand
Vince_vice is correct. Heat transfer is proportional to the temperature delta. In other words, the coffee cools fastest when the coffee is hottest. The rate of cooling slows as the coffee and outside approach the same temperature. So yes, it makes a difference when you add the cream.