What octane is E30 equivalent to?

E30 behaves like roughly 94–98 octane with better charge cooling than the number suggests: most of the practical knock benefit of race gas on a street budget.

Can a stock fuel system run E30?

Many can: E30 needs only about 10% more fuel volume than E10, which is inside the injector and pump headroom of a lot of stock systems. A tune calibrated for it is still required. Confirm headroom for your specific platform.

How do I mix E30 at the pump?

Split the fill between the E85 pump and regular pump gas; the right split depends on tank size, what's already in the tank, and the E85 pump's actual ethanol content. A blend calculator does it in seconds.

The E30 Blend — Octane Sweet Spot for Street Cars

Thirty percent ethanol is the street sweet spot; enthusiasts call it the poor man's race gas. Most of E85's knock benefit, a fraction of its drawbacks.

WHY E30 PUNCHES ABOVE ITS WEIGHT

Knock resistance doesn't scale linearly with ethanol content: the first 30% does a disproportionate share of the work. E30 behaves like ~94–98 octane with charge cooling on top, which is why dyno plots of 93-octane vs E30 tunes routinely show meaningful gains on turbo cars, while E30→E85 adds less than you'd expect.

WHAT IT COSTS YOU

MPG: about 7% vs E10, a rounding error next to E85's 25–30%. Check your prices on the worth-it page; E30 is often the best cost-per-mile ratio of any blend.
Fuel system: ~10% more volume than E10. Many stock injectors and pumps have that headroom; verify for your platform.
Tune: still required. The blend without the calibration is money left on the table (and risk added, on MAF cars especially).

MIXING IT

With typical summer E85 (test it, it varies) and E10 pump gas, E30 lands near a 1:3 ratio of E85 to gas. But the honest answer depends on your tank size, what's already in it, and the season, which is literally what the calculator solves:

THE E30 BLEND

WHY E30 PUNCHES ABOVE ITS WEIGHT

WHAT IT COSTS YOU

MIXING IT