I'm using the Castrol 5w40 in the E90 and F25. I know it's not your favorite. It's just that they didn't have the Valvoline in stock, and I like to keep with 1 oil for both, since the F25 takes a little over 5 quarts.
Should I just grab 2 bottles of the Castrol 0w40 and 1 bottle of the Valvoline 5w40? Or can I just run the Valvoline in both? I'll do an oil change on both in March when I do my fluid swaps.
Also, another question: how much brake fluid do I need for a brake flush? 1 liter? 2 liters? I'm not sure if you've done it yourself on your E90.