Those tires you have are too short. Your mileage figures for speed and distance are off by ~3% more than the error already there. Yes, speed makes a huge difference for fuel economy. Wind resistance is the major factor.

Dennis

----- Original Message -----
From: Niall Mac Caughey <nmacc@YAHOO.COM>
Date: Monday, April 10, 2006 6:27 am
Subject: MPG

> Hi folks, I'm a little late catching up on this thread.
>
>  I've had my 86 2.1 Digijet Westy for about 18 months, but I've
> only just gotten around to checking the mileage.  It wasn't that I
> overlooked it, more that I was afraid to find out how bad it
> really is.  The results were interesting.
>
>  On normal day-to-day driving including short highway trips at 75
> or so, I got 21.4 mpg; that's full-fat Imperial gallons, not those
> wimply lo-cal US ones.  It would be about 17.1 to the US gallons.
> I had to make a 220 mile trip on Friday over two-lane blacktop
> with no highway mileage.  For a change I planned in advance and
> left myself plenty of time for both legs of the trip.
>
>  Assuming that the brick-like aerodynamics of the Westy were a
> large part of the problem, I kept it under 60 for most of the trip
> and resisted the temptation to pass all the little old ladies and
> farmers I encountered.
>
>  I returned 28.1 mpg for the trip (22.5 US).  What surprises me
> is the improvement: 31%
>
>  For the rubber fetishists I should point out that I'm running
> 205/60x15 Fulda Carats fitted by the PO.
>
>  Regards all,
>
>  Niall
>