Hi all, haven't used my matic 525i for almost three weeks, car now hesitates a bit, engine even dies when I put it in gear to get going. Didn't have this problem before, tried switching to higher octane from regular unleaded, problem lessened somewhat. Should I just let her rip on a longish drive or must I change the plugs and oil? What are good plugs/oil for this model? Thanks, take care all!