The amount of fuel it drinks alone makes the price of engine oil insignificant!
Yes, very lengthy reads. It almost seems mandatory that every M Board/folder must have a "Why TWS" discussion. The "TWS only" arguments invariably lead from the oil being recommended by BMW and being adventurous unnecessarily exposes the car to risk of failure. It's great news to the dealerships if everybody kept their car stock. But sampling different kinds of oils is no different from slapping on aftermarket parts. Oils are in fact safer because they adhere to established industry standards of minimum performance criteria. Unlike say getting the ECU tweaked by a tuner.
Castrol has tie ups with numerous other manufacturers, Volvo, VW etc where they print the Castrol brand on the oil fill caps and/or cite it as a recommended oil in the manuals. The only difference with ///M is we seemed to have an oil 'designed' for us. Even that doesn't seem too convincing when it seems that TWS is used interchangeably with 'EDGE' depending on the sales jurisdictions.
http://www.lindvigs.com/obioban/EDGE_10W-60.pdf . Are we then now to conclude that we should be using Castrol EDGE? Is there really a pressing reason to ensure the 'right oil' goes into the car when even the manufacturer is so loose with nomenclature?
The ///M - TWS tie up seems more marketing driven in nature. Castrol is a good oil. But there are other equally good products out there. Until ///M tells me we should never put any other oil into our engines, I will continue to cast a wandering eye over other products... ditto non-OEM approved tyres.... ditto rims.... ditto.... ooops... LTA is looking.