[Eulenspiegel]

There's a station quite near me that sells ethanol-free gasoline, 92 octane (usually E10, 91 octane is the best available). Not cheap. What would be the benefits of regularly using this gas? Would it be worthwhile to occasionally fill up there?

[sinbad4]

Ethanol is sticky & corrosive and, left unchecked, would gunk up and corrode your intake system. To counter this, along with ethanol, detergents and oxegenates are added to negate the effect and keep your intake clean, reduce soot and carbon monoxide.

Ethanol is a easy way to increase octane levels. Lead was previously used, but is no longer allowed (for good reason). Without using these methods, extra refining is required and, hence, so is cost.

So.. is higher octane better. The answer is, "not necessarily." Higher octane reduces combustibility, this allows for higher compression, which allows for more air and gas to be used in each compression cycle. Lower octane will ignite prematurely in a high compression engine - before the piston reaches TDC (Top Dead Center). That premature combustion creates a compression wave that slaps the piston while still compression and creates a noise referred to as "knock". Besides the noise, it is hard on your engine and also reduces efficiency.

Bottom line:

1. Nonoxegenated fuels are better.
2. Do NOT use fuel with an octane rating lower than manufacturer specifies.

Sorry to be long and explain more than you asked, but info is related and good to know. I used to always buy the highest octane gas, even when my car only required 87 - thinking that this was somehow better. Sad waste of $$.