Oil change interval

[David C]

I'm not looking to start a debate, simply to understand how we get to such various results/recommendations.

As I said, my owner manual strangely doesn't state the oil change interval, however when I bought my car from it's second owner, she said he had it done every 10 000 km. I've done my first change at almost 12 000km, then second one at little less than 8 000km and now I'm at 8 200 km and about to go outside and change the oil for the third time. If we consider the driving conditions Toyota used in their interval specifications, I feel like the consensus is between 8 000km and 10 000km interval. However some of you mentioned going twice as much if not more using specific oils and filters. In my case I use synthetic brand name oil and (fair?) filters, so I believe I would fall into the 8 000km interval category, cost me $30 on oil and $10 on filter, so far I hit the mark every 6 months or so, aka I'd spend about $80 per year and the self labor of two oil change.

Would there be any benefit and reason I should go beyond the "regular" interval and use different oil/filter ? Please explain if so. Thanks