Engine oil Shell or OEM Subaru

dude stick to the engine oil grade mentioned in the user manual and fill shell synthetic of that grade

Shell advance long ride or power you have two choices for fully synthetic trust me dude once you try shell there's no going back castrol is the worst for Royal Enfield and motul is better suited for high compression engines like KTM etc

Oil being dark is a good indicator that you have to do an oil change. However, you shouldn't wait until it changes color to do it. Clear oil doesn't necessarily mean you can keep going.

It is well established that boxer engines want their oil changed and I do not think for a second that a visual inspection is valid for determining if it is time. Highly, **highly** recommend you change the oil per the manual without hesitation and regardless of what it looks like.

I run Shell Rotella T6 15W-40 diesel engine oil in my Versys. It has all the ratings necessary for a motorcycle engine and a wet clutch, and it is a quarter of the cost of bike oils.

Rotella T5, up to 14k in between changes per oil analysis. Great oil, never had any issues.

I've used Rotella T4 15w-40 in my 2008 6.7 Cummins year round in Canada. The ol girl has 700,000km (420,000 freedom units) and she runs like a top.

Rotella 5w-40, for no other reason than it is good oil that I can use in every internal combustion engine I own, including wet clutches.

Rotella 15w40 for mine. Never an issue and good oil reports for several hundred thousand miles.

Nothing wrong with LiquiMoly, but I personally find Shell Rotella T6 to be better. It is quite a bit cheaper as well.