Does premium gas do anything for a regular car?

If the manual says regular, premium is a donation to the oil company. Octane rating measures resistance to premature ignition, knock, not cleanliness, potency, or virtue, and an engine designed for 87 octane gains nothing from 93. AAA put this to the bench: in engines built for regular, premium produced no measurable improvement in horsepower, fuel economy, or emissions, while Americans burn billions of dollars a year on unrequired premium.

The word that changes the answer is required versus recommended. Required, common in turbocharged and high-compression engines, means use it; modern computers can pull timing to protect the engine on lower octane, but performance drops and sustained use is a bad bet. Recommended means the car runs fine on regular with a modest performance haircut, your call.

Where quality genuinely varies is detergent additives: Top Tier certified stations, most major brands, exceed EPA minimums at every octane grade. Buy the grade your manual specifies from a Top Tier station and the subject is closed.