Additive Friction Modifier

YY1 said
Valvoline has one as well.

I was a Castrol guy until I switched to Kendall in the 1990's and then to Valvoline when Kendall became too hard to find.

The 383 in my Super Bee was very good about "telling me" when it was time to change the oil, and I found the Castrol didn't last very long.
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I have of late been on the fence about Amsoil synthetic, but even though they say it's a 25k mile oil I have to wonder what ends up staying in my engine for 25k miles.
The price isn't too big a deal since my engine uses zero oil between changes.
Your thoughts?