I have a slight obsession with my MPG and I’ve been tracking it regularly using Fuelly.com. What I have noticed is now that the weather is beginning to get cooler the average MPG is getting lower. I expected this would be the case when I got the car so it’s not a shock to me. However since I was tracking the MPG anyway I decided to also track temperature too.
*Graph updated 22/02/2017
As you can see clearly, the average temperature (blue) has been dropping as we enter autumn/winter, and the average MPG (black) has also begun to drop as well.
So why does this happen? A couple of reasons actually…
- The engine runs less efficiently when cold and it takes longer to heat up, so extended warm-up times means it runs less efficiently and for longer.
- The engine must run even when its not moving the vehicle to generate enough heat for the climate control, so the vehicle occupants can stay warm.
- The hybrid battery is less able to provide power when cold, so it doesn’t help as much.
However it is surprising that on a short 15mi journeys, which is what 90% of my journeys are to work during the week, that I am still managing over 50mpg. Not bad for a 1.8L petrol! Some diesels would be lucky to see that, and a non-hybrid petrol wouldn’t come close.
I’ll continue to log this as we go into winter and it gets colder, and I’ll make a further blog post in the future. I do suspect that I will see a dip below 50mpg at some point when it gets colder, but for now it’s still impressive. The Passat, even for a diesel, was lucky to average 46mpg during summer and got even less in winter.