Idles rough @ 700 RPMs day after I had oil changed. I changed the oil because i have been idling car for 1 to 4 hrs a day for 2 months for warmth (homeless), and 'service engine light' came on. I've added fuel injector cleaner and oil additive to stop rough idling but its not working. Also added Chevron Techron gas. Accelerates great to hwy speed. Acts like it's missing at 4000 RPM in park. Some smoke under hood last night. Need cheapest alternative.