Response Surface Methodology (RSM) techniques are applied to develop brake specific fuel consumption (BSFC) maps of a test vehicle over standard drive cycles under various ambient conditions. This technique allows for modeling and predicting fuel consumption of an engine as a function of engine operating conditions. Results will be shown from Federal Test Procedure engine starts of 20°C, and colder conditions of -7°C. Fueling rates under a broad range of engine temperatures are presented. Analysis comparing oil and engine coolant as an input factor of the model is conducted. Analysis comparing the model to experimental datasets, as well as some details into the modeling development, will be presented. Although the methodology was applied to data collected from a vehicle, the same technique could be applied to engines run on dynamometers. These techniques allow for industry to compare test engine efficiencies under higher friction and heat transfer conditions, as well as the current standard coolant temperature conditions. This technique may also be used to develop BSFC maps for vehicle modeling when engine data sets contain variable engine temperatures. When combined with an engine oil/coolant temperature model, this technique would enable more accurate real-world prediction of fuel consumption for conditions outside of the standard test procedures.