Hello Everyone,

Maybe I should be posting this on the Fit Track forum
I did some engineering explained style acceleration tests to test the benefits of different octanes as well as initially fresh vs old gas. Which turned into the weight disadvantage.

The test was done in 36F even if different weather and night vs day on the same direction and stretch of road.

I found in second gear pulls recording 20-54mph

20-54 Empty tank 93 with A/C and rear defrost on 7.249
20-54 Full tank with A/C and rear defrost on 7.637
20-54 Empty tank 93 6.365
20-54 Full tank 87 6.904


.388s difference with 93 full tank vs 93 empty tank
60lbs of fuel/.388 seconds
~155lb/sec acceleration reduction

.539s difference with 87 full tank vs 93 empty tank



.2sec improvement in 20-54 from 93 octane vs 87 octane

~.9sec improvement in 20-54 by not using front ac and rear defrost

~2% improvement with 93oct over 87oct or more correctly 88oct

These are time improvements. Not sure what the actual hp improvement.

So there is an improvement but with a typical mileage for me of 15k/yr and 35mpg it is $100/hp. So for autocrosses its fine and may add a tenth or 2. but off season there's no reason, but if you do it out of love its on you.

Only thing I have to test is 87 octane empty.

Video here:

 

Your experiment is about right. 2-3 percent more HP and when your using premium your engine is running more efficient too using about .45 pounds of fuel per hour per HP Compared to .55-.60 pounds on regular. To many variables with fuel and temp corrections but very good info.