It's true that 100LL has lower density than most pump fuels. However that is also true of many race fuels.
Temperature plays a role in density specs but here's some published numbers to give some idea of the variations.
Specific gravities
100LL, 0.714 to .719
Pump Gas .74 typical
Sunoco GT .734
Sunoco GTX .764
Sunoco Standard .729
VP Vintage leaded .715
VP C9 .718
VP Blaze 100 .746
Race fuel info came from Sunoco Race Fuels and VP websites.
Pump Gas came from CRC E67 fuel Study (Durbin et al) and similar sources.
Av Gas from Fuel Mfc. Bulletins eg.
Shell Au 100LL pdf Distilation curve falls between typical street fuels and the race fuels I looked at. Posted a graph here:
https://www.tapatalk.com/groups/racingfu...579.html#p12657 I've used and tested 100 LL for a long time, I bought my first airplane in 1989. I've never used or tested 100LL from east of the rocky mountains so I'm not sure how 100 LL from there would test as far as specific gravity, all of the 100 LL I've tested has been right at .690, never above including when sitting during the winter in the airplane fuel cells inside the hangar
I use to buy and use 115-135 Avaition and even some 130-145 octane aviation fuel back when the airlines still used big HP piston engines in their airplanes, that stuff had a lot of lead in it
As far as the additives used in 100 LL it has a standard shelf life of up to 18 monthes
Todays pump swill usually has 90 days max life exposed to air n your car tank
OP as far as using 100LL in a race car be prepared to change your jetting, spark plug heat range and ignition timing to make the motor not hurt itself on 100LL
E85 is a much better choice in my opinion for todays world of drag racing
