Engine oil Shell or OEM BMW

Shell Rotella T6 15w40, has worked fine in my F800GS for 40k miles.

I would recommended shell ultra 15w50 . KV100 is 20 which is thick as fuck and won't shear down quickly. Mogul 7100 is thin and will shear down to 40 grade and internationally considered garbage oil. Shell is made of group 3+ base oil so its going to perform better.

Rotella 5w40 only. I daily and track mine

On an old e36, 5w30 full synthetic no matter the brand would often cause some leaks. Switched to some thicker Rotella oil made for diesels and suddenly no more leaks.

Worry less about the now old 502.00 spec than the actual oil itself. It's API SN/CF and has MB-Approval 226.5/ 229.31/ 229.51. Even though 505.00 and 505.01 are diesel engine specs, it should be fine in your older car. One of my go-to oils is Shell Rotella T6, which is specifically for diesels, but it's a great oil.

Its honestly all good, I ran Rotella T4 for a while, still good.

I'm a big Brotella Bro. I've used Rotella T6 in my WRXs, Miata, sport bikes, and dirt bike.

BMW used to recommend you changing oil basically every time you blink, back when consumers paid for 100% of all maintenance. But in order to be more competitive, they began offering 3 year included free maintenance on all new vehicles.

I suggest running Shell t6 5w40

Rotella 15-40. FTW