Originally Posted by jim383
So far 87 been ok but its about 1.5 mpg behind our 91 with normal driving and at wot 91 is a must to get the full all out performance.
I can agree with you on that.
I still think the performance issue might have something to do with a slight uptick in mpg between 87/89 octane. If I tow a long distance or take a long trip I will use 89. Other than that I find no real difference.
The only issue I have is the trade off in price per gallon. I pay .20 gallon more for 89 vs 87 and the trade off is not there for increased MPG.
Now that gas above is all labeled up to 10% ethanol.
Now if you would like to see a real good improvement in mpg try 100% gas, that is no ethanol added. I use to use it all the time when the difference was only .10-.12 a gallon. Now its .25-.30 gallon and not worth it for the benefit.
I am not sure how much benefit you are gaining from using 91 vs 89 instead.
I know My local station sells 87 ethanol, 87 100% gas, and 91 100% gas. Using either of the 100% gas will boost my MPG by 2+mpg.
I know in Illinois they are required to label the gas content if it contains ethanol. A label like "up to 10% ethanol" for each grade that contains it.
They can use less ethanol of no ethanol under that label. If either of those two things happen your mpg will improve. I think that is one of the issues I find when comparing mpg.