I've noticed that some gas stations are indicating that they are adding 10-20% ethanol in their gas. I know that regular gas has some ethanol, but not as high as 20%.

I know that ethanol will raise the octane. However it also has a lower stoichiometric ratio than gasoline (9.x vs 14.x), so it takes more of it to make the same power.

I have a street flash, that I got 2 years ago on 94 octane (back when it was available). Will today's lower octane, combined with the new ethanol % affect may original tune?

 

Of course it has an effect - however with pump gas tunes there is more than enough margin or saftey to afford for this variation in fuel

AL

 

Does ethanol decrease the quality of Gas? How does it hurt?