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Re: [Phys-l] Hybrid mileage

If it runs more it charges the batt. more completely then when hot the E is recycled. Of course, not 100% efficient, but not so poor that it's the explanation, I think.

bc noticed much diff. between his '06 and his '08 versions

p.s. viscosity also not -- oil is very hi-tex viscosity more nearly constant w/ temp.

On 2010, Jan 05, , at 12:54, Shapiro, Mark wrote:

Part of the loss of mpg in the winter for a hybrid (and all other cars) is that the engine has to run longer to bring the catalytic converter up to temperature to meet emission reduction requirements. And the engine has to run more to keep the converter up to temperature.

Mark Shapiro
From: [] On Behalf Of Richard Tarara []
Sent: Tuesday, January 05, 2010 12:45 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Hybrid mileage

I've been thinking about the same topic, but applied to all cars. Remember
that a Hybrid is still 'mostly' an internal combustion engine vehicle. The
initial viscosity of the oil in the engine is a factor and (I suspect), all
those cold parts may be a bit tighter than when they are warm parts. The
temperature of the air coming into the engine itself may be a factor too.
However, it would seem to me that once the engine is warmed up, unless the
intake air temp is a big deal, most of the differences should
disappear--which is where I still have questions. I suspect that the
battery performance in a hybrid has temperature effects too--just not sure
what they are.

Rick Tarara
free software at:

From: "Robert Yeend" <>
Sent: Tuesday, January 05, 2010 3:16 PM
To: "Forum for Physics Educators" <>
Cc: "Nancy Seese" <>
Subject: [Phys-l] Hybrid mileage

A colleague asked me why it is that she consistently gets 6-8 mpg
less in the winter than summer with her Prius Hybrid. Her mechanic
said that that was "normal," but gave no explanation. Nor can I. She
said that she uses the heater in the winter about as much as the air
conditioner in the summer.


Bob Yeend
Forum for Physics Educators
Forum for Physics Educators