Hybrid Fuel Economy Drops with the Temperature

In my review of the Honda Civic Hybrid, I mentioned that my fuel economy was nearly 10 mpg lower than the EPA estimates, and wondered if it had to do with the cold temperatures that week. Could freezing temps have an effect on the batteries or the electric motor? Or was I imagining things?

I checked in with my informal panel of experts, the Oregon Electric Vehicle Association, whose members drive hybrids, plug-in hybrids, and EVs. According to these road-tested experts, I wasn’t imagining things, but I didn’t have the whole story.

First of all, Oregon adds ethanol to the gasoline in winter, which reduces fuel economy by about 4%, which I had forgotten about. Second, the snow and gravel would increase friction, which would lower the mpgs. Hybrids also lose energy heating up the whole engine and keeping it warm. Hybrid drivers can combat the drop in mpgs by turning off the defrost and heat while idling to get the gasoline engine to shut off as it does in more pleasant weather.

Several OEVA members also mentioned that everyone, hybrid and conventional car drivers alike, have been driving more carefully in the snow and ice. The techniques we use to avoid sliding into parked cars are the same ones that save gas overall and extend the range of electric vehicles:

• Start very slowly
• Take your foot off the gas far from the stop sign
• Keep a huge gap between your front bumper and the next car’s rear bumper

One final word of caution: Hybrids are usually fitted with low-rolling-resistance tires to maximize the mpgs. These are pretty awful in winter weather, so if you’ve got a hybrid and live in an area that sees a fair amount of fluffy white stuff, it’s probably worth it to invest in a set of snow tires.