What's the best filesystem battery-wise for laptops?

[Bob Raymond]

This question may have been asked before, and I apologize if it has, but
my friend has a problem with battery life on his laptop.  He only gets about
fifty minutes to an hour in Linux, while in WindeXP, it's more like two
hours.  One thing I notice in Linux is that there's a lot more HD useage
going on.  Could this be because of the ReiserFS that's on there now?

He's coming over Sunday so I can install SuSE 8.0 (to replace 7.3) and I
noticed XFS is one of the options.  I know from personal experience that
it is faster than ReiserFS, but how good is it on the batteries, or is
the filesystem even the problem?

Thanks,

Bob Raymond

specs:

Sager NP5620
Intel P4 1.8ghz
ATI Mobility Radeon 7500
30GB 5400 RPM HD,
Part. table:

8mb /boot /dev/hda1
15GB (approx). / /dev/hda2
256mb (approx). swap /dev/hda3
14GB (approx). /windoze/C /dev/hda3

256mb PC2100 DDR