This is going to be a little on the long side for me. Straight from the Blender.
Gasoline's are blended with high octane stocks such as Toluene @ 106 oct, Heavy Reformate @ 102 oct, Whole Alkylate @ 91 oct, MTBE was being used but has been removed from the market. Toluene is used mainly for Unleaded Supreme because of the expense. Lead was used in the past for two reason's, First was lubrication but guess what Second Lead in small quantities make a great octane booster so less of the expensive blend stocks were needed and money was saved.
Regular Leaded Gas in the old days contained 0.01 gram's of lead per gallon.
Unleaded Gas today contains a MAX of 0.008 gram's of lead per gallon.
( Av Gas Chevron LL100 has much more lead so it is measured in ml. instead of gram's. I couldn't find any conversion charts for lead additives but 1gram of water is = to 1ml maybe someone else on the site can convert it more accuratley.)
Going on, Av Gas has 1.97 ml with a MAX of 2.0 ml per gallon thats about 250 times the amount in gas today. Av Gas is not blended for Octane though its blended for Lead Content , Lead Uniformity, Distillation, Vapor pressure, Sulfur , Gravity, etc...The Octane number is checked but not posted. Chevron LL100 Av Gas has an Octane number of 120-124. WOW
Blending your on Octane numbers is easy, gallon for gallon just add the 2 numbers and divide by 2.
EX. 1 gal of 87 oct. gas + 2 gal of 93 oct. gas =273 divided by 3 = 91 oct.
So 1gal of 124 oct. Av Gas + 4 gal of 93 oct. supreme =496 divided by 5 = 99.2 oct. (Plus the Lead content alone added to the unleaded gas would boost the octane number so your end result would be higher.
ANYWAY if your going to use Av Gas it doesn't take as much as you think and you can minimize your lead by not overdoing it. (Tip the older guys suggest putting a cap full of Marvels mystery oil in with every five gal you mix.) Working in General Aviation for 16 years now I have put Av Gas in just about every car I've owned. I never ask about these numbers so in the future I will mix it for Lower Lead content. If anyone has any questions I'll do my best to get an answer to you.
Check out this site for a Tetraethyl Lead additive for boosting octane, http://www.4unique.com/fuel/lead_sup...supreme130.htm

 

I too have been using avgas in all my vehicles for the past twelve years. I have only had one problem and that was my own stupidity. I burned a cat out on a Toyota Avalon but I was running straight Avgas.

George S.