Lik

Pretty sure that Honda only recommends regular gas (87 octane) for the Fit, so if you don't do any performance driving, and you don't really push your car all that hard (stay in the high rev zone), regular gas (lowest octane level at the pump) is probably good enough.

The thing to watch out for is whether your engine is knocking. If you've been keeping up with regular maintenance, this shouldn't happen. But should it happen, it'll tend to do so on hotter days when you push the car harder. The ECU is supposed to retard timing to prevent knocking, but it can only do so much, and if something is wrong, the engine will still knock. When it does, you'll heard a knocking / pinging sound coming from the engine. It should be fairly obvious if it is really happening.

I used to be a fan of ethanol-blended gas, but increasingly there has been evidence that, under current production methods, it isn't nearly as good an alternative as it was once thought. So now I tend to shy away from it.

-Lik

Lik

While ethanol only contains roughly ~60% worth of the energy found in gasoline, bear in mind that ethanol-blended gas only contains 10% ethanol at most. That means with a 10% ethanol blend, the blended gas should only contain 5% less of energy. That 5% difference could easily be lost in the midst of variation in driving conditions la.

-Lik