When I was a practicing A&P in the late 80's/early 90's I was running a 10.0:1 (via milled 302 heads) 318 with headers, AFB, dual plane Wieand, 284/.484 purpleshaft. I'd run 25% 100LL with 85 unleaded (4 gallons of 100LL in a 16 gal tank). Engine really liked that with 37* (6kft) and I could bring it all in by 2500 without problems. I'd have to back off to 34 for 91 unleaded, and couldn't stand on it off the line to avoid detonation. Sure smelled good. I could fill it up with that combination for $15.

I have no performance metrics to share.

So, when I was working in a repair station on Continental and Lycoming airplane engines that ran 10LL exclusively, at 2500hr overhaul we'd knock the plug out of the crank snout and from behind the plug back to where the cranks got solid right before No.1 brg, would be packed with lead. Leather aprons, rubber gloves up to our elbows and face shields were worn while we used aluminum scrapers to literally get the lead out and it all had to go into a hazmat bin.

Lead in the blow-by mixes with the oil and through some act of physics and engineering would accumulate in that part of the crank. I was always told that there is too much lead in 100LL to run it uncut in an automotive application, and that its exclusive use (uncut) on the street would cause long term durability problems due to oil formulations and no place for the stray lead to collect, which would cause it to pack piston ring grooves as well as mucking up the PCV system.