It has nothing to do with the size of the engine, etc. It's the machining precision. Oil can withstand 9k miles before you need to change it, that's what Mobil 1 states on the jug.

The real reason to follow the manual intervals is because every engine is built differently and around 3k miles oil is contaminated with 3% gas from blow by, whic his not the case on BMW and AMG due to tighter seals or whatever else their engine design is the culprit.

So mitsubishi engines get oil dirty. Period. No knowledgeable person would tell you "modern cars" and "syntetic oil" in one phrase.

So stick to schedule.

 

Same as above - you can run unicorn tears there but if your oil contains 3% gas it's lubricating properties are severely diminished.

 

That's a perfect interval but I'd swap it out if I was going to HPDE or autox or had let my car sit for more than a month with a lot of temperature fluctuations.