Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A calculation based on the chemical energy of gasoline shows that a car should be able to go 100 miles on a gallon of fuel. When the car was driven on a test track, the car only went 25 miles on a gallon of fuel. What accounts for most of the difference?
the waste heat from the combustion of fuel in the engine
Inefficiencies in the car's engine and other systems.