Couldn't see this discussed after a search, so here goes:
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.
Fuel efficiency in winter
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Re: Fuel efficiency in winter
Running the heater, once the engine is warm, puts no additional load on that engine, unlike running the a/c to cool.
Colder denser air increases available power and efficiency.
You're right to call bullshit on the claims being made, just as TVs don't take 20% power just by being on standby.
These "facts" are just lies, or at best a distortion of carefully selected truths.
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Colder denser air increases available power and efficiency.
You're right to call bullshit on the claims being made, just as TVs don't take 20% power just by being on standby.
These "facts" are just lies, or at best a distortion of carefully selected truths.
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Re: Fuel efficiency in winter
I can’t remember the exact percentage but years ago I drove from the south coast of England to Glasgow and it lashed it down with rain the entire journey. I mean lashed. And I mean entire journey. It was very odd. But my car and the van I was in convoy with absolutely hammered the fuel consumption, to the point where I was sure I had a fuel leak or under inflated tyres until I got to the destination and the other driver said the same thing to me and we checked the vehicles.
We both assumed it was the slight increase in resistance and the energy consumption of the huge wiper motors being on for over 8 hours. May have been wrong but it only ever happened on that journey.
This anecdote would be better with facts and figures I agree, but if I had to guess our fuel consumption was way above 20% more.
We both assumed it was the slight increase in resistance and the energy consumption of the huge wiper motors being on for over 8 hours. May have been wrong but it only ever happened on that journey.
This anecdote would be better with facts and figures I agree, but if I had to guess our fuel consumption was way above 20% more.
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#174’s journey: viewtopic.php?f=104&t=78506
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Re: Fuel efficiency in winter
You can pick any figure you like depending on your motivation. Want to gloss over the problems of EVs? 20% suits you, sir.
I looked at this a long time ago when I was involved with running a large vehicle fleet in Germany, where summers are hotter and winters colder than here. Fuel consumption on a fully warmed-up car is only marginally different in U.K. temperatures, colder air giving greater drag and engine efficiency being largely unaffected. There are also contributions from lower tyre pressures, winter fuels having additives that reduce mpg and greater road congestion in winter. The difference depends heavily on the fuel and vehicle, but especially with Diesels (additional kerosine in winter) you can expect up to 2-5% in the U.K.
The main reason that winter mpg is lower is simply the longer warm-up time, with the associated greater viscosity of engine fluids, gearbox fluids and various bearings.
I looked at this a long time ago when I was involved with running a large vehicle fleet in Germany, where summers are hotter and winters colder than here. Fuel consumption on a fully warmed-up car is only marginally different in U.K. temperatures, colder air giving greater drag and engine efficiency being largely unaffected. There are also contributions from lower tyre pressures, winter fuels having additives that reduce mpg and greater road congestion in winter. The difference depends heavily on the fuel and vehicle, but especially with Diesels (additional kerosine in winter) you can expect up to 2-5% in the U.K.
The main reason that winter mpg is lower is simply the longer warm-up time, with the associated greater viscosity of engine fluids, gearbox fluids and various bearings.
Ian
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Now back to one, a white R3. Gone but not forgotten: 04 Tit Grey 231, 06 Copper Red Evolve (231), 09 VR R3, 10 Aurora Blue R3, 06 Black PZ; RX87 13BREW project car ;-( ; 04 White with Greddy turbo conversion ;-(
Buying a used RX8 turbo is like marrying a stripper.
Beware - older people may be cr@p drivers but they can afford better lawyers
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Re: Fuel efficiency in winter
I don`t know about others but I have noticed that on a damp day with very low temps my RX-8 is one of those cars that seems so much better to drive and years ago I had a chipped Escort RS Turbo and that also always felt better in those conditions.
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Re: Fuel efficiency in winter
What WildMan said. Longer warm-up, and the early morning defrost has a large impact on the multitude of short journeys that pervade car use. Once everything is at steady state, you can benefit from colder intake temps.
Ploughing through standing water on the other hand has substantial kinetic cost that will translate to higher fuel consumption on a really wet day.
Ploughing through standing water on the other hand has substantial kinetic cost that will translate to higher fuel consumption on a really wet day.
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Re: Fuel efficiency in winter
Yes, the increased rolling resistance for driving through even a small amount of standing water is amazing and goes up by close to the square of the road speed.
However, it rains in summer too...
However, it rains in summer too...
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Re: Fuel efficiency in winter
I just looked into winter blends of fuel and apparently that is a thing, even in the UK. But the winter blend in the UK isn't much different to the summer blend. Unlike in somewhere like Russia where the winter blend is subjected to much lower temperatures.
Winter blends are also only for diesel fuel... so don't apply to the RX8.
Winter blends are also only for diesel fuel... so don't apply to the RX8.
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Re: Fuel efficiency in winter
That's also consistent with the only reliable data I can find regarding seasonal fuel consumption differences, which is all about truck and van fleets.
The study for the Police Chief Constable's concluded that any difference was within the variation of the data, when looking at petrol vehicles.
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The study for the Police Chief Constable's concluded that any difference was within the variation of the data, when looking at petrol vehicles.
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Fuel efficiency in winter
An interesting video to watch
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Re: Fuel efficiency in winter
And destroys my economy in summer too. My old company car would drop from mid 50’s to mid 40’s at motorway speeds, if it was possible/safe to maintain 70.
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Re: Fuel efficiency in winter
There are several factors at play in the winter that affect fuel economy, firstly the car will take longer to reach optimum operating temperature so will run richer for longer, oils will have an increased viscosity creating drag, tyre pressure will reduce increasing rolling resistance(it's surprising what a few psi will do) then of course the intake temperature will be lower so the ecu will add additional fuel as the air is more dense
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Re: Fuel efficiency in winter
That last one means more power is available, but doesn’t increase fuel consumption.
You're also much less likely to be running the A/C compressor, which is a major saving.
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You're also much less likely to be running the A/C compressor, which is a major saving.
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