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Re: [Phys-l] Hybrid mileage

Very useful information - thank you! Between the running at higher rpm's to
warm up and the lower energy output of winter gasoline it seems to explain
the 3-4% difference I see in my mileage in the winter.

The reasons listed so far, however, do not explain the 10-15% differences in
mileage for the Prius that have been reported today. I still can't help but
think it has to do with battery efficiency in cold weather. I know I should
know, but do not, the details of why batteries die faster in colder
temperatures. This, I'd imagine, has an impact on the Prius' winter
performance explaining why the mileage decrease is substantially more than
that of gas only vehicles.


-----Original Message-----
[] On Behalf Of B. Esser
Sent: Tuesday, January 05, 2010 4:50 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Hybrid mileage

On Tue, 5 Jan 2010, WC Maddox wrote:

"Remember the oil companies put oxiginaters in in winter for easier
starting. Cuts down on power. They also don't care if you use more.
Witness their profits. Nor do the FEderal gov't - 18.6 cents per gallon
tax and states, anywhere from $.07 to $.30 per gallon tax."

Summer blends of gasoline run about 114,500 BTU's per gallon with a
federally mandated range of 113,000 minimum to 117,000 maximum.
Winter blends average 112, 500 BTU's per gallon with a variance from
108,500 to 114,000. The summer/winter average difference is 1.7%.

If you are in an area where RFG (reformulated gasoline) is required then
difference between summer/winter blends can be as much as 3-4% based on a
Wisconsin study.

Bruce Esser
Physics Teacher
Marian High School

Forum for Physics Educators