| Target | E85 | Pump Gas |
|---|
Mixing Your Own Ethanol Blend
Blends like E30 have become popular with enthusiasts because ethanol resists knock and cools the intake charge, letting a tuned engine run more timing. Since pumps rarely sell exactly the blend you want, many drivers mix E85 with regular pump gas to hit a target. This tool tells you how many gallons of each to add for your tank size.
E85 Is Not Always 85 Percent
Despite the name, pump E85 legally ranges from roughly 51 to 83 percent ethanol, and stations dial it leaner in cold months so engines start in winter. That swing changes your final blend, so the only way to be sure is to test the ethanol content with a cheap fuel tester. Enter the real percentage for an accurate mix.
Why Ethanol Content Matters
More ethanol means more knock resistance and cooling, but also that the engine needs noticeably more fuel volume, since ethanol carries less energy per gallon. That is why higher blends demand a compatible vehicle or a tune and adequate injectors. Use this for planning the pour, then confirm fueling with a wideband sensor.
Frequently Asked Questions
What blend should I run?
Only what your vehicle or tune supports. Flex-fuel cars handle up to E85; a non-flex car needs a custom tune and hardware even for modest blends like E30.
How do I know my real E85 percentage?
Use an inexpensive ethanol test kit or a flex-fuel sensor. Seasonal and regional variation makes the pump label only a rough guide.
Does more ethanol make more power?
On a knock-limited or boosted engine that is tuned for it, often yes, thanks to better knock resistance and charge cooling. Without a supporting tune, it mostly just costs fuel economy.