Gas Mileage

cobram at cobram at
Mon Jun 25 15:00:39 EDT 2007

You can also drive down the highway, set the speed at 60 MPH and measure
the time it takes to drive between mile markers. One mile at 60 MPH takes
60 seconds. If it is not 60 seconds between mile markers, the difference
is the speedometer error.  If you have a GPS with speed readout, get the
GPS at a steady 60MPH and see what your speedometer is reading and what
the trip odo reads between mile markers.  These will give you ballpark on
how far off the speedo is.

I knew I should have book marked it, but someone had posted a URL of an
online speedo compensation table or calculator a while back.  Anyone
still have the url?  It would calculate the RPM (Revolutions Per MILE) of
the OEM tire vs. larger tire and give the speedo error.

Those original mileage figures for CQ are pretty good.  We had a thread
like this on the V8Q list, the V8Q had an EPA of  14 city, 18 highway, so
the car never had decent mileage to begin with.

We come into the world naked, screaming and covered in blood. Why should
the fun end there?

"Jason Kohls" <jasonkohls at> writes:
> 18 city/24 hwy
> With the 17" tires, would the rolling circumference be great enough
> that the odometer would be off enough to render my mpg calculations
> this much?

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