Originally Posted by jud149

My previous car before my '11 LS460 was an '02 Mercedes CL500. When these first came out MB, too, said the tranny fluid was lifetime only to later back off and suggested changing at the 40k mile level. Also of interest pertains to fluid refill instructions following a drain which, like Lexus, indicated how critical the fluid temp was in obtaining the proper fluid level.

Being the skeptical person I am along with the fact that I just couldn't see a tech standing around waiting for the fluid to reach the proper temp (this could easily take 20 minutes or more at idle and the MB dealer labor rate here in S. Florida is around $200/hr.), and since I was about to change the fluid myself, I thought I'd run this procedure by a MB tech and service mgr. In doling so, both kind of smiled/laughed and said they didn't follow it as it wasn't really necessary and just checked the fluid cold.

FWIW, I later changed mine and just replaced the exact amount of fluid removed and the tranny ran a smooth as before the change.

Anyway, just my 2 cents on the subject.

Originally Posted by bclexus

Having done drain-and-fills myself I can assure you that they drained right at 4 quarts.

The formula's math is correct... 4 Qts removed / 10.9 Qts capacity = 0.367 or 36.7% or rounded to 37% of old fluid that was removed...with the reciprocal amount (63%) of old fluid remaining in the transmission. Therefore, 100% - 37% = 63% of old fluid remaining with one drain-and-fill. Accordingly, each successive drain-and-fill is calculated as follows: The 63% of old fluid that remained after the first drain-and-fill times another 63% (or .63 x .63 = .397 or 40% old fluid remaining) after two drain-and-fills. And, three drain-and-fills equals .63 x .63 x .63 = .25 or 25% old fluid remaining, and four drain-and-fills equals .63 x .63 x .63 x .63 = .158 or 16% old fluid remaining, and so on and so forth...

I would recommend doing 3-4 drain-and-fills over a period of time in lieu of a [so-called] flush. Also, I would always replace the drained fluid with the manufacturer's recommended ATF.

Originally Posted by swfla

I gave things some thought. The math formula is going to be be very close to actual results. So, no need to spend money on another Blackstone test. Thanks again for your help and contribution.