Most regular 87 octane gas in the U.S. has about 10% ethanol , usually sold as “E10.”

Quick Scoop

  • At most stations, 87 octane = E10 = about 10% ethanol and 90% gasoline.
  • Federal rules and typical pump labeling limit standard 87 octane to no more than 10% ethanol.
  • Some areas sell “Unleaded 88” (E15, 15% ethanol), which has a higher octane (88) because of the extra ethanol, not because the base gasoline is radically different.
  • In certain regions you may also find 87 octane that is ethanol‑free (often labeled “E0,” “recreational fuel,” or “non‑oxygenated”), but that has to be clearly marked on the pump.

Why it matters for your engine

  • Most modern cars are designed to run on E10 with no issues in performance or reliability.
  • Small engines (lawnmowers, boats, older equipment) can be more sensitive to ethanol because it attracts water and can cause corrosion or fuel‑system problems over time.
  • If you need less than 10% ethanol , look for pumps labeled ethanol‑free/E0 or a clear ethanol percentage label; stations are required to disclose the blend (E10, E15, etc.).

In everyday terms: if you’re filling up with normal 87 octane regular at a typical U.S. station and there’s no special “ethanol‑free” label, you’re almost certainly getting about 10% ethanol.

Information gathered from public forums or data available on the internet and portrayed here.