Instead: Hydrate with H2O. One of the best measures you can take to avoid kidney stones is to drink plenty of water, leading you to urinate a lot. So, be sure to keep well hydrated, especially when engaging in exercise or activities that cause a lot of sweating. It's Not Just the Oxalate.
You didn't say what year or model BMW. The service intervals vary a huge amount between models a years. BMW built since the mid-1980s have a service indicator. You should change the oil when the service indicator tells you to. On BMWs that specify synthetic oil, you should change the oil when the indicator counts down to zero or once a year whichever comes first.
Consider how this applies to service intervals. If the manufacturer recommends an oil change every 10,000km, then an oil change every 8,000km would comply to the cheap insurance argument. Servicing only slightly more often doesnât cost much more. What about, once you decide to change the oil every 8,000km, you discover that itâs now only a small incremental price increase to change the oil every 6,000km.