With the demise of 80/87 avgas, I bought a gallon of TCP and will
start adding that to the 100LL that I must now buy.

However, scouting around the internet I found something that claims to
be similar in function but safer: decalin. Here's a blurb from
Aircraft Spruce. My questions are, has anyone any experience with
both decalin and TCP, and how do they compare? And, in spite of the
last sentance below, can decalin be used beneficially in certified
aircraft engines?

"Scavenges Lead in aviation fuel after combustion to prevent lead oxide
buildup on valves but still allows the lead to perform the anti-knock
function prior to combustion.

"It is an excellent additive for auto conversions, where it reduces
buildup on oxygen sensors and plugs. If you have to use 100LL, then
this stuff is for you. Prevents valve seat erosion from valve seat
micro welding. It is equivalent to TCP.

"Does not contain volatile solvents so it is safe to ship and safe in
the cockpit. You can carry it with you for out-of-town airports.

"Easy to use graduated measuring and dispensing resevoir built into the
bottle. No messy syringes!

"Tested and stable down to 0 degrees F.

"Decalin TCP is not approved for use in the engines of certified
aircraft."