MPG Reality Check

[Michael]

--- In WanderlodgeForum@yahoogroups.com, "jackcj7" wrote:
>
>
> Hardly in the same league as the "Deezel" birds, but the mileage in our
1973FC31 with the 391 gas engine bounces around between 5 & 6mpg... This is
making the loop from SoCal to the Seattle area, over to Spokane and Billings,
and home through either Denver or Salt Lake City... We always tow our CJ7
fitted with freewheeling hubs at all corners... Most of the time, we can roll
along at 60, but on some hills a bit slower. On the Grapevine and Raton quite a
bit slower, more like 18 to 20...Just find a big, slow 18 wheeler and fall in
behind him...
> Jack Smith
> 1973FC31
> SoCal
> .
> --- In WanderlodgeForum@yahoogroups.com, "freewill2008" wrote:
> >
> > Finally, after 7 years, I filled the fuel tank to the top, drove 1015 miles,
and filled it again. The 167 gallons calculates to about 6 MPG.
> >
> > The method has plenty of potential for error. The odometer reads low and I
don't have a GPS. I used the Google mileage plus 5% to account for wrong turns,
finding RV sites, etc. The route was Brookings, OR to Q by way of Hwy 101 and
Malibu, CA.
> >
> > The tank is so big that I figure the fill could be off by as much as 10%.
If the fill-up were 10% low, the MPG would have been 6.7. If the fill-up were
10% high, the MPG would have been about 5.5.
> >
> > Other details: 1984 FC31 with California 210HP turbo 3208. Road speed
about 58 MPH. 4.89 gears. 11R22.5 Michelins at 105 and 95 PSI. Towing a Honda
CRV. Air filter has about 5000 miles. The air intake is the enlarged version
designed for the 250HP turbo engine. Never blows any black unless I make an
operator error.
> >
> > To achieve the 10 MPG sometimes suggested for the FC, my mileage estimate
would need to be off by almost 700 miles, or the fill-up would need to be off by
almost 70 gallons.
> >
> > I'd be interested any anyone else's MPG observations and the method used.
> >
> > Bob Griesel '84 FC31 WLII WA
> >
> Do the calcs when home from a trip, fill @ the same pump @ local truck stop,
add up all the fuel used and divide by miles traveled. My FC w/charge air
cooler gets 6.5/7.0 every time. Odo verified by mile sticks. Do the whole trip
average as that's the best way to figure real mileage. Cruise @ 63 most of the
time. Tow 240D or F-150.