Not sure I agree with JffGRY above, but lots of threads on this. Owner's manual says Premium. The accusation of ALL auto companies being "in bed" with oil companies is conspiracy crap. Bottom line based on other threads is this: you'll pay one way or the other, Premium will cost you more at the pump, Regular will cost you more in lost MPG's, and maybe potential repairs?
Just go with Premium, especially with increased ethanol percentages.
@moderator , good job on thread merge!

@demark1 , I don't totally agree with your first paragraph, but totally agree with your 2nd. Having owned 2 LS's and an Acura RL, burning through brake pads is a luxury sedan thing, likewise rotors; I've had them smoothed once in between brake jobs.. They do NOT like to be braked hard! But cost versus anything equivalent today....please, no comparison.

 

Regular fuel noticeably slows the car down. It loses noticeable torque and oomph down low that affects the driving experience.

I put the required fuel in my vehicles but sometimes I'll run rotgut gas in it in a pinch, an LS430 really does need premium fuel.