I have a Porsche Boxster with a "new" IMS bearing and have Motul 8100 X-cess 5W40 installed. Car is driven monthly & I am trying to determine should I change oil by millage or by time in engine.
This is an excellent question, I had a BMW M6 from 2006, and it was an oil eater. But the factory said that I should change the oil every 3,000 miles with full synthetic.
There's a catch though, the harder you drive your vehicle... the quicker you'll need to change it. I had dirty and dark oil in my M6 after 2,000 miles and it was time to change it. Normally though, it would be around 3,000 miles when the next change needs to happen.
You can drive a car 1,000 miles per year and actually not need to change the oil. Given you don't let it sit for too long (like months...). Using oils that keep your engine running well is crucial, that factors into the overall quality of your engines performance and longevity of that quality.
( attached the picture of my M6)