I asked the Lexus parts guy today and he said there was no difference between 2004 and 2005, so I guess K&N is just slow updating their web site.

 

I've filled my brand new 05 GX up twice - used 87 (regular) both times. Here are my results so far. I drive short trips on the weekend (horrible mpg) and a long commute with a mix of "highway"/city Mon-Fri.

1st fill-up:
Computer: 17.4 (I was so excited!)
Manual calc: 16.4 (hmmm...)

2nd fill-up:
Computer: 16.9
Manual: 16 (I'm beginning to see a pattern here)

I'm going to look into the K&N filter - sounds promising!

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'05, Silver, Nav, DVD

 

I mentioned this a couple of years ago. With all of my 3 GX's starting in 03, the trip computer has always shown a much better reading then actual.