system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 What is the difference between regular and premium gas?
gpt
The octane number describes how high pressure the fuel will self ignite at. Engines which produce higher compression require fuel with higher octane number to combust without knock ( harmful sporadic ignition before the carefully timed spark from the spark plug).

Also, fuel has additives designed to clean your engine from soot and provide some lubrication an protection for the surfaces inside the combustion chamber and exhaust.

Premium gas has more and better additives usually combined with higher octane number.