I have a 2000 chrysler neon with 200 000Km on it. I have been using 5W-30 Castrol regular oil in it from the time i bought it when it was at 100 000Km. the car didnt even come with an owners manual so i don't know what it should have anyways a friend told me it should be running 5W-30 because he also had a neon. so i run that oil type all year round. A few years ago i noticed on cold mornings the engine bangs allot for a couple seconds after starting. I am guessing its the thick oil not getting up quick enough. I was considering switching to synthetic but a person from another forum told me it might do more harm than good at that millage. What would you guys recommend? Should i switch to synthetic? or go to a lighter oil for the winter time? I really like the information on this site and a lot of it sheds a lot of light on oils. I found it to be very helpful in understanding how oils work and the classification process. So the question remains what to use?