Mixing octanes. 93 shortage due to Irma

I'm an IT guy so chemistry isn't a strong suit. Hurricane Irma has brought lots of shortages to the supply chain obviously. 

Most of my cars run on 93 and we have a chump race next weekend as that car runs on 93 as well.

I can find plenty of 87 but 93 is in short supply. 

The tracks typically carry 98. So my question is: does mixing octanes do anything? Does it make things better or worse? For you chemist and subject matter experts, what do you recommend? 

As with anything I'm mainly concerned about the race car lol

If you had the internet you could probably look it up

http://www.sunocoracefuels.com/tech-article/mixing-fuels-calculating-octane

[(Xgallons x Xoctane) + (Ygallons x Yoctane)] / (Xgallons + Ygallons) = Resulting Octane

Most gas stations with three octane choices dont have three tanks of fuel in the ground. They have two, 87 and 93. The midgrade that comes out of the pump is a mixture of the two.

gearheadmb said:

Most gas stations with three octane choices dont have three tanks of fuel in the ground. They have two, 87 and 93. The midgrade that comes out of the pump is a mixture of the two.

you learn something new everyday...

I have been driving my TDI and Cummins almost full time due to that. 

In reply to Zomby Woof :

have you used 3G lately to do much of anything is hard. Cell service is spotty and I'm still without power. GRM is my phone browser home page. Thanks though 

Stampie said:

[(Xgallons x Xoctane) + (Ygallons x Yoctane)] / (Xgallons + Ygallons) = Resulting Octane

At least as a first approximation - I've heard this isn't quite 100% reliable. Should be "good enough" if the 98 octane at the track isn't anything too bizarre.

I'd expected this thread to be about grabbing a couple gallons of toluene from the paint store.

The RAV4 needs high octane.  Really high octane.  You know, for on ramps and E36 M3.

All I can get around here is 91 octane.  There's one Sunoco place that has 93 octane for (currently) four bucks a gallon and 98 octane for (currently) about 8 bucks a gallon. 

So I was thinkin... If I took like 9 gallons of "no alcohol" 91 octane and added in 1 gallon of E85, or 8 gallons of 91 straight gas and 2 gallons of E85, whatever, (maths), would I get something closer to 93 octane for less than a $1.50 cost premium over the race gas?  Most of the 91 octane stuff sold is labeled as having 10% ethanol anyway.

8 gallons of 91 octane E0 and 2 gallons of E85 should get you to around 93 octane or a hair better, depending on the exact mix of the E85.  You'll be at about 17% ethanol from that mix (assuming the E85 is really E85, it tends to get closer to E70 in the winter in most places).  

You can drive a car with low octane as long as you are light on the throttle.  Just listen for the rattle and let up.   Did that years ago.

I haven't noticed any shortage yet in Cincinnati area, which is nice, as the GTI is not happy on 89 or lower.

Any modern engine with knock sensors can run whatever octane you want.  The knock sensors will detect knock well before it is audible to you and retard timing.  May take a tank or two of premium before it slowly advances back to max power though.

Modern GM's, or at least the ones I'm familiar with, automatically run the more advanced timing map on startup, then revert back to the lesser one after a set number of knock events.

NEALSMO said:

Any modern engine with knock sensors can run whatever octane you want.  The knock sensors will detect knock well before it is audible to you and retard timing.  May take a tank or two of premium before it slowly advances back to max power though.

Understood.  The GTI is just doggy on a tank of lower octane, especially in hot weather.