I found few articles saying that Mercon SP is same as ZF lifeguard 6.
User fun2drive, sent samples of both ZF lifeguard 6 and Mercon SP to Blackstone laboratory for analysis. And the result states that both were very similar. Has anyone used the Mercon SP on their automatic 6 speed transmission? I was looking to use this on my 05 x5 4.4.
Mercon SP ($8) at local parts store vs ZF lifeguard6 $20. That's more than half off.

Automatic Transmission Fluid (ZFLifegaurd6=Ford Mercon SP) - Bimmerfest - BMW Forums