Cold Start Impact on Vehicle Energy Use

This paper assesses the impact of the cold start phase of light duty vehicle use on energy use based on a review of large set of vehicle emissions test data from Canadian and U.S. Government databases. The data indicate that, at 24°C test ambient, a 20% increase in fuel use is measured in the “cold” Bag 1 driving compared with the “hot” Bag 3. Lower ambient conditions increase this penalty in a linear manner such that at the -6.7°C test condition, the penalty rises to 40-80%.

The paper then integrates the laboratory tests data with vehicle demographic and usage data gathered from consumer driving studies. Included in this data are results from a small pilot survey in Vancouver, which directly measured instantaneous fuel consumption of vehicles in consumer use. These data sets were then used to estimate the total “extra” energy used during the cold start phase of driving. The analysis indicates that in Canadian urban centres, up to 25% of the total fuel use is due to cold engine effects.