Question

why do you think we need to put energy into the cylinder system to get the fuels (like gasoline or diesel) to react with oxygen?

Explanation:

Fuels like gasoline or diesel react with oxygen in a combustion reaction, which has an activation energy. The energy input (e.g., from a spark in an engine) provides the activation energy needed to start the reaction, overcoming the energy barrier for the reactants to transform into products. This is related to chemical kinetics and thermodynamics in Chemistry, a subfield of Natural Science.

Answer:

We need to put energy into the cylinder system to provide the activation energy required for the fuel - oxygen reaction to start, as chemical reactions (like fuel combustion) have an activation energy barrier that must be overcome for the reaction to proceed.