April 13, 2024

Effects of Preheating on Vehicle Fuel Consumption and Emissions Found to be Minimal, Study Shows

A recent study conducted by the University of Eastern Finland and Tampere University, published in Applied Energy, has revealed that the benefits of preheating vehicles during cold winter conditions have minimal effects on fuel economy and emissions. The researchers specifically focused on cold start emissions and their relationship to preheating.

The study conducted a measurement campaign in Finland, during which outdoor temperatures dropped as low as -28 degrees Celsius. The researchers aimed to replicate typical commuting scenarios, including urban and highway driving, as well as stops at intersections and traffic lights.

Vehicles were driven on the same route under three conditions: after a cold start, preheated, and with the engine already warmed up by driving. The results showed that cold starts were particularly challenging for diesel-powered vehicles under cold winter conditions. The engine coolant took nearly the entire drive (13.8 km, about 19 minutes) to reach its optimal operating temperature (>60°C). The vehicles used in the study were equipped with electric or fuel-powered preheaters.

While efficient preheaters helped warm the engine coolant before starting, they did not significantly accelerate the process of reaching the optimal operating temperature. Higher starting temperatures mainly improved vehicle comfort by providing a warmer cabin and preventing window frost. Additionally, preheating can potentially reduce engine wear during cold starts, according to car manufacturers.

The study found that overall fuel consumption was slightly lower (10-20%) when the vehicle was driven after being warmed up compared to after a cold start. However, only two out of the six vehicles studied, both equipped with fuel-powered auxiliary heaters, showed small fuel savings due to preheating. Even in these vehicles, preheating only resulted in a fuel consumption reduction of less than 4% compared to cold starts.

It is important to note that the calculated fuel savings did not take into account the fuel or electricity consumption of the auxiliary heaters during preheating. When considering the fuel consumption during preheating, the post-preheating drive resulted in 26-37% higher overall fuel consumption than after a cold start. Preheating also had an impact on overall emissions, as it led to higher emissions compared to cold starts.

These findings suggest that the use of fuel-powered auxiliary heaters cannot be justified solely by better fuel economy or reduced emissions in cold temperature driving. However, it is worth considering that preheating may have long-term benefits for a vehicle’s lifespan, such as extended engine oil life and longer engine durability, although these factors were not examined in this study.

Assistant Professor Panu Karjalainen of Tampere University highlighted that preheating did not significantly affect particulate emissions either, which is consistent with the observations on total fuel consumption. The number concentration of particles exceeded regulatory limits for new vehicles by up to a hundredfold. This discrepancy may be attributed to the fact that regulations only consider solid particles larger than 23 nanometers in size and apply to emissions measured under warm conditions. The measurements conducted under cold winter conditions showed high concentrations of smaller particles, some of which could be liquid.

In conclusion, the study suggests that preheating vehicles during cold winter conditions has minimal effects on fuel consumption and emissions. While preheating may provide certain benefits such as improved comfort and reduced engine wear, it is not a significant factor in achieving better fuel economy or reduced emissions. Further research is needed to explore the long-term effects of preheating on engine oil life and durability.

*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it