Hehehehe.
We'll be all over the chart on this. Here's my take:
1. I drive about two miles to work. Two miles back home for lunch. Two miles back to work. Two miles back home after work. Repeat -- five times per week. Other drives are similar short trips to the store and such. Anything longer than that is "weekend fun time" out on the open road. I consider this to be ultra-ultra-ultra-ultra-ultra-severe service. Most every time I drive the car, I might well not be allowing the engine to get as warm as it would really rather get. This should build up "gunk" in my oil as fast as about anything else you could do with a car.
2. I figure a dino oil change costs about $25. I figure a synthetic oil change costs about $50.
3. I probably don't do quite 12,000 miles per year -- maybe even under 10,000. So, "twice a year" would be a 5,000 mile oil change interval.
4. But, given my ultra-ultra-ultra-severe usage, I'm just gonna do it "every three months, whether it needs it or not." And I'm gonna do it with synthetic oil, which "breaks down" less than dino oil does.
5. OK, big whoopie, I'm wasting $100 bucks a year (that's a whopping $8.33 per month) to make very damn well sure I'm getting the crud out of my engine before it has any chance to do any harm.
6. This has gotta be the best "hundred-buck insurance" to help ensure long engine life I could ever spend.
Works for me -- I've been doing this for over a decade now with my vehicles.
Oh, and to go along with the concept of
GET THAT GUNK OUT OF MY ENGINE, I changed my oil the first time at 1,000 miles. "Every three months whether it needs it or not" thereafter.