I used them too, mostly Mobil1 Synthetic.
OP, the brand of oil that you use is not as important as how often you have it replaced. I change engine oil every 7.5K mi. I know others who use regular oil on their E39 for years and change it every 3K mi without any problem to the engine.
Your brake might just have uneven deposit on the rotors. Before you replace them, I would do a proper bedding and see if that fix the problem.

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00 E39 DINAN S1 //M5 (82k miles)
06 E53 DINAN 4.8iS, born 2/18/2006 (126k miles) http://www.xoutpost.com/bmw-sav-foru...s-my-dslr.html
90 Straman Z32 TwinTurbo Convertible, (1 of 44 ever made) 5 speed, 444rwhp/451rwtq
01 360 Novitec Spider F1 (26k miles)