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From: jimv@apollo.uucp (James Vienneau)
Newsgroups: net.auto.tech
Subject: Winter gas mileage
Message-ID: <2b96d3b6.46b9@apollo.uucp>
Date: Mon, 27-Jan-86 15:01:02 EST
Article-I.D.: apollo.2b96d3b6.46b9
Posted: Mon Jan 27 15:01:02 1986
Date-Received: Wed, 29-Jan-86 04:06:29 EST
Organization: Apollo Computer, Chelmsford, Mass.
Lines: 25

> I have noticed that my gas mileage drops by 15-20% every winter

There has been several replies to this posting, so I can no longer resist
to put in my 2 cents.

It would seem to me that fuel is energy. So, what we are really saying is
that the engine consumes 15%-20% more energy in cold weather.

Now think about a cold engine with a mineral based oil in it. First the engine
engages a choking device to enrich the mixture. The amount of time and the extent
of this enrichment is a high percentage of the waste of energy. Now if the majority
of usage is short trips I would expect this percentage to be normal.

Second, the mineral base oil is probably much thicker at these temperatures. This
results in increased friction, requiring more energy to produce the same effort.

Third, The 30 degree (for example) engine including its oil and coolent must be 
raised to the 190 degree, or so normal operating temperature. This also requires a
significant amount of energy.

I believe it is the combined effect of these three factors that contributes to the
loss of mileage in the winter. You can see that the longer the average trip, the lower
the percentage drop should be.

Well thats it, do I get change from my 2 cents? :-)