87 vs. 91 Octane MPG and Performance

I should have been more specific. These days, if they are raising octane by adding ethanol, then energy content will be slightly less.

At least here in California, they have replaced MTBE with ethanol... unless they use more toluene or something else.

From the internets.

Makes sense to my brain, but please correct me if I am wrong again.

 

It's a fuzzy area but my impression is that California regular and Premium are both 10% ethanol since 2010.

 

Interesting. What is it specifically we are paying more for in 91 octane?

 

You are absolute right. I totally agreed.
Don't waste money for an engine which can burn the 87.

 

Beats me, probably the same stuff we paid more for after the lead was taken out and before the corn lobby corn holed us.

 

All I run is 87. Runs great. I average low 50's with plug-in kit off.

 

Here are a couple of fairly good articles on the subject:

Regular Versus Premium Gasoline
The Straight Dope: What's the difference between premium and regular gas?

The bottom line is still, use 87 octane in your Prius unless you are in the Rocky Mountain states then it's OK to use 85.

The difference in energy content between regular and premium is negligible. Depending on what is used to blend them one or the other may be slightly higher under some conditions.

 

I accept your clarification...good info!

 

A typical USA refinery has to "bake a cake" with many different ingredients to make gasoline. So the higher octane ingredients are considered more valuable (more expensive to make) and those are segregated into the higher octane blend. I would think the higher octane stuff tends to contain more energy, that's why I questioned you when you said premium has less energy. Agree with you that higher octane, if gotten via ethanol addition, is less energy.