Date:         Thu, 9 Dec 2004 22:14:15 -0500
Reply-To:     "Daniel L. Katz" <katzd54@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Daniel L. Katz" <katzd54@YAHOO.COM>
Subject:      Re: 55 to 65 mpg in a diesel vanagon?

list:

in my experience, claims of very high mpg values are usually due to
inumeracy, not only in the sense of inaccurate arithmetic, but also a
failure to recognize when a result is physically unreasonable.

more than once i've had this discussion, and got to root of the problem
very easily by working through the arithmetic myself. for example, suppose
somebody claimed 55 mpg for a 1.9 l gas vanagon. well, i know 18 mpg is
reasonable, and happen to also know that 1/18 equals 0.055... , so i
suspect that the ratio was reversed, and the extra 0's were just ignored.
an example of a correct and reasonable calculation is:

miles driven/gallons consumed = 1000 mi/55.6 gal = 18.0 mpg

note that units accompany the numbers, and by carrying the units along, it
helps keep the calculation straight.

dan

On Thu, 9 Dec 2004 08:49:12 -0800, Mark Drillock <drillock@EARTHLINK.NET>
wrote:

>This summer my wife and I went on a 3000 mile trip in our diesel Westy.
>I carefully tracked the fuel consumption at EVERY fuel stop. There was
>as much as an 8 mpg swing between the best and worst tank fulls. Should
>I ignore the lows and brag only about the highest? I'd consider that to
>be wrong. Should I use only the first 2000 miles where we drove more
>slowly on country roads? Fine, as long as I say that is what I am doing.
>On the interstate at 65 mph into a strong steady headwinds I saw 20 mpg.
>Driving in a more lazy fashion on back roads at 50-55 I saw 28 mpg. At
>various points in each case the numbers must have been much higher and
>much lower but I can only average it over the distance between fill ups.
>
>Anyone can contrive conditions under which their fuel mileage will be
>very good. If I coast down the Grapevine Pass for 10 miles I can claim
>100 mpg in any vehicle. Of course when I turn around at the bottom and
>drive back up I may get only 10 mpg. So 10 miles down, 0 gallons, 10
>miles up 1 gallon, 20 miles total, 1 gallon = 20 mpg.
>
>It is deceptive to claim the highest mileage you ever see as your true
>mileage. Tell us what average MPG you see over 1000 continuous miles at
>typical  speeds or at least disclose what conditions existed when you
>got the absurdly high figures. You were asked 9 months ago to explain
>your 39 mpg claim. Now 9 months later you say you were finally able to
>verify 39 mpg on a recent trip. What MPG did you get during the missing
>9 month period?
>
>
>Mark
>82 Westy 1.9TD, DK tranny
>
>Gnarlodious wrote:
>
>>Entity Paul & Becky Oliver spoke thus:
>>
>>
>>
>>>I saw a vanagon on ebay that the owner claims gets 55 to 65 mpg. It has
a
>>>diesel engine? Is this possible?
>>>
>>>
>>No.
>>I get 39 MPG and they call me a liar. If  got 65 MPG I wouldn't even
mention
>>it.
>>
>>-- Gnarlie
>>
>>
>>