Good morning Benjamin
You may want to take a look at these test done by Auburn University ( War Eagle )
These test showed my 93 Dakota will get 1.3 miles per pound of wood and almost 21 miles per gallon of gasoline when driven at speeds between 50 and 55 miles per hour.
One thing I would like to note is I have updated the gasifier design with hopper cooling tubes which I think improves performance and millage even more .
Gasoline in my area is 2.20 a gallon .
As far as the cost of my wood fuel is hard to calculate. I always use scrap wood for fuel that has no other value . I do add my labor to chunking the wood but I enjoy the work . I know that is hard to explain but is is kinda like going out for a jog . Some people would think it is work while others might enjoy it ?
I do use some diesel while chunking the wood but the machine I use I think would chunk a ton of wood with a quart of fuel !!
When I gasifie the wood grown on my farm out driving and then come back home to dispose of my ash and char I am just using the solar energy from the farm by bring the nutrients right back where they come from .
Here is another reason that makes it hard for me to calculate wood cost . 95% of the wood I use in my gasifier comes from scrap sawmill slabs. These logs were hauled in to my mill from other land owners . I use the scrap in my truck and deposit the ash and char on my farm ( free fertilizer )