New cheapish oil and a NEW filter, the good lord only knows what is in the current one. Also remove the cam cover and pour fresh oil on the cams and cam chain -- while in there, check your chain tension. Fire it up, get it up to temperature (oil hot, not just coolant) and then drain the oil and replace the filter again. Use medium quality oil this time. If everything runs well so there is no need for the engine to be opened up then change the oil and filter again in a 100 miles or so. Use the good stuff this time. Now you can do regular oil changes from there on in.
I followed this procedure except I use good oil every time, paranoid I guess.