In an attempt to make it's customers feel better about the plumetting of battery range in EVs during winter, my EV rental company said this week in an email: "All vehicles, whether they run on gas or kilowatts, become less energy-efficient in cold weather. The typical internal combustion engine vehicle can see its gas mileage drop by around 20% in the cold".
20% reduced petrol economy in winter sounds like a lot to me. I've never noticed an mpg reduction in cold seasons. So I hit the search engines and found wildly varying estimates of reduced winter mpg, but they all agreed with the above statement. The vast majority referred to or lifted from this page by the US Department of Energy and EPA (both 'Green Agenda' affiliated) giving reasons for their own claim of roughly 15% reduced mpg in winter: https://www.fueleconomy.gov/feg/coldweather.shtml
Some of the reasons given are plausible. Such as cold engine fluids. That seems valid (for about the first 10 mins of a journey).
They also say that cold air being denser increases aerodynamic drag. I'm just not convinced the change in drag across a 20 Celsius temperature band really impacts mpg that much. The increase in air density even at freezing looks slight... to me anyway.
Other reasons they give are just silly driver errors, like underflated tyres reducing mpg and idling the engine on a cold day before driving it off gives you 0 mpg. They've seriously factored those into their sums.
They mention 'winter fuel' having less energy too. I assume that this is a regional thing and not applicable to the UK? Or do they change the blend here for winter
So that was pretty disappointing. I've yet to find any real research on this. Specifically related to the efficiency of combustion at lower ambient temperatures once the engine is warm, as that doesn't take long. Without the stuff that muddies the water like leaving a car to idle or letting tyres deflate.
I imagine that the increased use of lights and wipers will put some drain on the alternator, or that heating the cabin might use more energy than blasting the air con in summer. But are they tangible amounts? (Besides in summer I drive around with the windows fully down so that others have to listen to my overly loud music, less so in winter)
Do any of you folks have any wisdom on the topic? Are our RX8s really 15-20% less efficient in winter? Or is that rumour and groupthink? If it's true, any tips to increase/maintain mpg in winter? Other than the 'Turn the heater off' advice that my EV rental company advised in their email. EVs get cold inside with no gearbox or exhaust to sit on. Blessed be our warm transmission tunnel.
