you can rent a compression tester from any auto parts store. you just plug it into each of your spark plug holes and crank the motor (take out fuel pump/ignition fuses) and that might help diagnose the oil on the plugs
---------- Post added at 10:02 PM ---------- Previous post was at 09:53 PM ----------
i just thought of something... pull your water pump cover (the 4 bolts and cover by your motor mount) and see if the water pump/balance shaft chain is still tight and on there. if not, there's your problem. happened to me once, my car hated life
agreed on that for a compression test. Ensure that your within specs to it. If one cylinder is lower than the rest, check your valvetrain, can be a broken valve spring, lifter, or broken lobe. If 2 cylinders (companion or opposing), check your head gasket, may have cracked. If all, then its your bottom end, aka crank.
2009 Cobalt LS XFE U74
Mods: K&N Typhoon Intake, Option Cat-Back Exhaust, Cosmo Short shifter, Maxxim Ahead 17X7's, MPx shorty antenna, FE5 Strut/shocks, Tein S Techs, Moog endlinks, Moog spring seaters, ZZP shorty header, LSJ downpipe, LNF front grille