I have read and seen many articles regarding car warm-up time from a cold start in the morning. Each article varies, some say I can wait about 10 seconds, some say 1 minute, others 3-5 minutes... So which seems to be the most optimum.

My car cold starts at 1500RPM, and then goes to 1000RPM in about 1 minute. My car uses 5w-30, instead of the recommended 5w-20.

Any ideas?