I have a rural property, 25 miles out. There is plenty of firewood there. Has anyone done the math on what is more efficient, a large truck hauling a large load (very low miles per gallon but bigger payload) or a smaller vehicle that may take two trips to haul the same amont of wood?

I cannot do the math without knowing how many MPG each vehicle gets. You also need to figure in tire wear, your time, etc. For maximum efficiency, EVERY trip out there, for whatever reason,, should bring a load home. That way, you never need to make a trip just to get firewood. A pick-up will haul about one half cord. One trip per month means 6 cords per year, without making a special trip.

Large truck, one load. I know this because the government here allows mileage (okay, it is in kilometers, but same idea) for different vehicles. The mileage for our diesel pickup is nearly the same as for our six ton truck.

But, if you are traveling to the site to cut, and cut one load a day, well it is cheaper just to return with that load. That is what I used to do when I cut firewood to heat the home. I bet this is the best idea.

But then again, I am talking a large truck that can hold 3,000 bf of lumber - or about 50 sheep.

Mileage on a large truck doesn't drop that much when loading, I suspect it does on pickups. Not sure.

how about a 1/4 (or 1/2 or 3/4) ton truck and trailer? your mileage will be a little less but you'll be able to haul much more. leave the trailer home when you're hauling just a truck load and don't ever press hard on the accelerator. will yield good results mileage-wise and offer some hauling versatility to boot.