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Octane

A fuel's resistance to detonation. Higher octane raises the knock limit and lets you run more advance — match it to your compression ratio.

Demo build: this panel is locked

The octane dropdown is available in the full game. See Demo vs Full Version.

What it is

Octane (RON) rates how well a fuel resists auto-igniting under pressure and heat — its resistance to knock. It is not a measure of energy content; a higher-octane fuel doesn't carry more power on its own. What it does is raise the knock limit, giving the tune room to use timing that would detonate on lower-octane fuel.

In Engone, octane raises the knock limit by 1° per octane point: the limit is 40° + RON − 87 before the other penalties.

Why it matters

Octane and the engine must be matched:

  • High compression raises cylinder pressure and temperature, which lowers the knock threshold — these engines need high octane to run their intended timing.
  • Engines that are not knock-limited gain little from premium fuel; the knock limit isn't what's holding them back.

Run too low an octane for the build and you're forced to pull timing (losing power) or risk knock. Run higher octane than needed and you've simply spent money for advance you can't use.

How to tune it

Pick the octane that matches your compression ratio, then tune the timing table to it. If you switch to a higher octane, you can add advance toward MBT; on lower octane, you must retreat.

Changing octane does not change your spark table. Re-check the knock-limited cells yourself.

Rule of thumb

Set octane to match the fuel you'll actually run, then tune timing. Tuning on premium and then filling with regular is a recipe for knock.

On a boosted engine

Engone currently simulates naturally aspirated engines only. For background: a boosted engine packs far more air into the cylinder, so the tune changes — target lambda moves richer (to cool the charge and protect against knock), ignition advance comes down in the boosted cells, compression ratio is usually lowered, and higher octane matters more. See Boosted Engines (Background).

In the game

Octane is the FUEL OCTANE dropdown — IGNITION page → right column → KNOCK DETECTION card — with the options 87 / 91 / 95 / 98. The engine base's recommended octane is the default (I4 91, V8 91, V12 98). Octane is saved in your tune.