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 car may produce many forms of energy from the fuel it uses. Which indicates that a car does not use fuel with 100% efficiency?
The car engine gets hot.
The wasted energy appears as heat, noise, and exhaust gases.