you should note that a gas engine does not convert all that 33kWh of energy into mechanical energy. a gasoline engine has about a 25% conversion into mechanical energy. https://www.fueleconomy.gov/feg/atv.shtml . diesel might be a bit better than a car but it's city driving by nature.
just heat alone is the largest waste product in a car or truck
A tank of gas is still a tank of gas, regardless of what it gets used for.
Energy in = energy out + waste + energy stored
The truck is barely storing anything on average, so what you've described is energy out and waste, but the calculations to compare the truck to the landfill was done on Energy in - the amount of gas that it needs to be filled with.
For the same total job, you could raise or lower how quickly the truck goes through a tank of gas, but that variance has already been averaged out
just heat alone is the largest waste product in a car or truck