I replaced me broken speedometer so I can keep track of my mileage again.
17.8 mpg was the latest ... took about 1 month to drive 300+ miles. I drive it on weekends for fun and drive it to work on fridays (36 mile round trip)

( 56 f600 with 94 cummins 6sp + 4sp aux dana 80 with 3.31 ratio)

photos in my gallery

 

Wow! Awesome job with transplant. How long did that project take?

 

I would expect great mileage, those trucks are very light!

 

Thanks
It took a year and a half of saturdays In the backyard.
search in this forum
( 56 f600 cummins conversion ) and you will find my build thread. Also photos in my gallery

 

My f600 weighted 8400# before the cummins conversion I expect it to be over 9000# now

 

I looked at your gallery photos and they too were excellent.

 

My 09 F550 weighs 13,660# pounds empty with a V10, so your class 6 truck weighs only 2/3 of the weight of my class 5. Very light in my book!

 

My 2006 F-450 reg cab 6.0 12 foot steel bed weighs 9800lbs empty.

The gearing you have will give the mileage I don't know what model Cummins you have 12 or 24 the old 12 would give you the mileage if you kept the engine at 1800 or less.

 

It is the 12 valve with the bosch p7100 inline pump

 

Really surprised an F-600 weighs that much,I had a '55 F-750 with Daybrook dump body that weighed 8300# and a '64 F-600 with 5 yd Marion dump that weighed 7800#
My 2000 F-350 with a topper and a few tools in the back weighs 9500#

 

All steel fire body with diamond plate step&bumper, 154" wb, steel water tank.

 

I'm alway amazed at how much the newer trucks weigh! Must be the freaking electronics!