Jets [and turboprops] don’t use leaded fuel. Many of the small, piston-engined airplanes do, but because current FAA regulation forces them to, not because of a lack of regulation.
This is about to change though with G100UL finally being approved. https://gami.com/g100ul/g100ul.php.
Absent an STC (Supplemental Type Certificate) to change that, there is a regulation that those engines in certified aircraft have to use leaded fuel to be airworthy (legal) as airworthiness requires both “in condition for safe operation” and “in conformance with its type design”.
GAMI is pursuing an all-model (or many, many model) STC for their fuel to remedy this, but it’s a regulation issue currently.
Small jets do indeed use jet fuel but have a terrible efficiency proposition when ran at even 50% capacity, which is not the standard use case.
For track or drag usage, running on the ragged edge makes more sense.