Does it affect the octane rating? And if it does, in what way?
Yes - didn't know this, huh, this sucks.
To answer your question directly: Yes, it significantly lowers the octane rating. Why the Octane Drops
Ethanol isn't just a filler; it is a high-octane component. Pure ethanol has an octane rating of approximately 108 to 110. When refineries mix it with gasoline, they often start with a lower-octane "sub-grade" base (around 83–85 octane) and rely on the 10% ethanol to boost the final product to the 87 octane you see at the pump.
When you "wash" the ethanol out with water, you are removing the very ingredient that was doing the heavy lifting for the octane rating.
You’ve got the right idea on the "how"—the water-extraction method (also known as phase separation) is a common DIY trick for small engine enthusiasts. But while pulling the ethanol out is easy, what's left in the container isn't exactly the high-quality fuel you started with.
To answer your question directly: Yes, it significantly lowers the octane rating. Why the Octane Drops
Ethanol isn't just a filler; it is a high-octane component. Pure ethanol has an octane rating of approximately 108 to 110. When refineries mix it with gasoline, they often start with a lower-octane "sub-grade" base (around 83–85 octane) and rely on the 10% ethanol to boost the final product to the 87 octane you see at the pump.
When you "wash" the ethanol out with water, you are removing the very ingredient that was doing the heavy lifting for the octane rating. The Impact
The Math: If you start with 87-octane E10 and remove all the ethanol, you are typically left with a "base" gasoline that tests somewhere between 82 and 84 octane.
Engine Knock: Most modern car engines are designed for a minimum of 87 octane. Running 83 octane can lead to pre-ignition (knocking), which can damage pistons and rods over time.
The "Lean" Issue: Ethanol contains oxygen. While removing it might seem better for old rubber seals, your engine's carburetor or fuel injection system is tuned for the volume of the E10 mix. Removing 10% of the volume can sometimes cause the engine to run leaner than intended.
Thanks for the explanation. I heard that it would change the octane rating but didn't know the details. Here in Belgium, it is 95 or 98 octane; that's a big difference compared to 83 or 85.
Not that I’ve read, but if you remove the corn shit, you do get more btu from the same amount. But you have removed some volume, thus 1gal becomes less than one but do more to compensate.
How do you dispose of the off junk? Not that I care and would pour around my slab to mitigate weeds.