I checked on unmodded Exp2 install with Hollywood Explosions pack downloaded from here, no problems, all effects show up, including explosions of fuel tanks, also bomb hits, planes fires, flak, smokes, ground hits, midair explosions, napalm, whatever I had chance to see during several test strikes and all, BUT I've blown several fueltanks at opfor airbase and apart from initial explosion, there was no secondary MediumOilFire effect so far. You may be right something's wrong here Piecemeal
edit:
All titles merged with both expansionpacks, ran thru Exp2 executable; Dx10 Win7, all graphics on high/unlimited except shadows and mirrors turned off, drivers up to date