We have a diesel Citroen, granted we do not use it to pull, but it is extremely economical. PRoblem here is that the initial cost of diesel engine is so much higher than for petrol that you must drive it forever before the economy equals the cost. And when you fill up here, diesel is now as expensive if not more than regular petrol.
Many have them here because they go through water better than petrol engines, but we don’t have to worry about the cold.
The land cruiser runs on lp gas and petrol. The lp gas is dirt cheap and clean burning. Don’t know how that would go for heavy hauling. It is fine with our small trailer.