Quote:
Originally Posted by Homeslice
The only reason they say Castrol is "required" is because Castrol did something for BMW that will never be disclosed. And 10W-60? That's going to result in a lot of deposit-causing additives being used in the formula, because additives are the only way they can achieve such a big spread between the 10W and the 60.
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That oil wasn't originally spec'd for the engine. If I remember correctly BMW had some VANOS system failures due to oiling issues. They asked Castrol to develop the oil to meet the specific requirements of that engine. The VANOS system operates partially off oil pressure. I'm guessing the lower viscosity oil didn't create enough oil pressure to properly actuate the VANOS system which resulted in failures.