My observations are that automatic transmission maintenance is often neglected or ignored completely. In my opinion, auto transmissions are the weakest element in modern drivetrains. This is not to say they are not reliable for say 100,000 miles. But a neglected transmission will not have nearly the life of the motor.
I change transmission fluid at 50K mile intervals. It isn't cheap. The 4.6 liter Genesis has a variant of the German ZF 6HP26 transmission. This transmission was first used in 2001 by BMW in their 7 series, and by Audi in 2003 in their A8. I found a place in California which sells a fluid change kit:
http://www.thectsc.com/index.php?p=product&id=186&parent=8.
The kit is $221.95.
First off, what you say about taking care of your transmission is true.
I saw this same thread in the Jaguar Forums, as the XJ Jags use the same transmission.
The price of the LifeGuard6 fluid is a LOT cheaper than the Hyundai fluid, which is about $75. a quart. If I knew that the LifeGuard6 Fluid was not tinted red, I would just buy enough Liters to change the fluid, and not buy the pan/gasket or filter because even though the 6HP26 used in the Genesis 4.6 is probably the same as the 6HP26 in the BMW or Jag, it may not, we just don't know if there are any small changes to the pan or gasket, etc. If the LifeGuard6 is tinted Red, I would not use it as long as the Genesis is in Warranty, because the ZF Fluid is Clear, and if the day comes that the transmission gives you problems, and Hyundai sees that you have red fluid in there, they will decline the warranty. BTW, dealers don't "fix" the ZF Transmission found in the 4.6. They exchange it with a new one from Hyundai who then takes the old transmission apart, or Hyundai sends the old one to someone (perhaps ZF) who takes it apart. If the wrong fluid in in there, goodby warranty. If anyone does buy the LifeGuard6 Fluid, make sure that somewhere on the bottle, it states that it meets the M-1375.4 spec that Hyundai and ZF call for, and I would save the empty bottles, just in case there is ever a transmission problem while under warranty.
To those of you who buy a Previous Owned (re; Used) Genesis 4.6, the transmission warranty is much less. (Can't remember how much, but somewhere around 60k miles). In that case, just use Mobil-1 ATF in the transmission. Costs much less. My buddy with a 2005 XJR (Supercharged) that uses the exact same transmission, did a pump and dump with the original Jag/ZF Fluid, and used the Mobil-1 Full Synthetic ATF. Transmission shifts great, and is very happy with it. (He really did three pump and dumps, all in a row, to get rid of most of the original fluid). He made sure that after the last pump and dump, he checked the temperature of the fluid when he checked the fluid level, to make sure it was not underfilled or overfilled.
If I were to buy either a used Genesis 4.6 or a used Jag XJ, I would change out the fluid with the Mobil-1 Full Synthetic ATF Fluid.
BTW, I understand the guys in the BMW and Mercedes Forums that use the exact same 6HF26 Transmission say the same thing about using Mobil-1.
Note that this thread is for the Genesis 4.6 that uses the ZF Transmission. It is NOT for the Genesis 3.8 that uses the Aisin Transmission.