Does premium fuel actually make a difference in cars that don’t specifically require it, or is it marketing hype?

The truth is, most people (and even some car guys) have no idea what octane is or how it works. To put it as simple as possible, ‘Premium’ fuel with its higher octane of 91, 93 or 94 typically. The higher the octane, the more resistant the fuel is to combustion. When an engine is designed, the manufacturer will recommend the octane to be used based on the engines combustion cycle timing & compression ratio. It’s recommended because if you don’t follow it (too much or too little Octane) can cause premature or late fuel ignition which can cause a ‘knock’ which can rob power, cause damage, carbon buildup & overheating. The good news, is that we live in the modern age where virtually all new cars past the mid 90’s started coming with ‘Knock Sensors’ as standard. So the ECU can detect in real time & adjust timing to make pretty much every car run well enough.