MPG Reality Check

[freewill2008]

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