Of today's balls for heavy oil,,,,The Ebonite Mission X is tough to beat!
Brunwick Nexxus looks real sweet also.
Regards,
Luckylefty
PS I think for league slick crowns with dry to the side there are many great ones by most companies as listed by Tommy Boy.
PPS On heavy long flat oil like Avabob(I point) I have also used the pearls to very good effect the Battle Zone Bullet was a killer for me along with the above mentioned track Spell. (higher rg for both balls took out the belly(midlane) that kills a bowler on Flat heavy oil).