"Greasing" springs is a good way to end up with a broken spring. Leaf springs are supposed to have "pads" at the end of each leaf which helps prevent squeaks.
A quote from a spring company
Starting in the mid 50’s the steel used to make springs began to change over to SAE 5160 which does not like petroleum based products, grease/oil/etc.
Petroleum based products deteriorate the steel causing premature failure.
In the 40's and early 50's springs packs were actually designed so they could be greased but they used an entirely different steel and today's spring packs actually rely on friction between the leaves to prevent them from sagging, even to the point of having a reverse arch.
If the squeaking annoys you then do as the old-timers do, turn up the radio. Or make sure your next tt has torsion axles.
If they just started making noise this means that the dust/dirt has dried out. When it rains the squeaking will go away.