Pretty simple...
In the early days for big capacitors, they were actually called oil baths to stay cool.. Ignition coils are essentially a step-up transformer and things can get hot especially for some of the later iginition systems.. And like many other auto/electronic components these are being outsourced from China..

I can't confirm this but since we have been traveling/sourcing electrical components from China for > 25 years I would wager a beer that they have reduced the amount of oil used internally...

Juts my $0.02...