I have a 2006 HiHy, not a Lexus, but the resuls should be similar. I found that 40 PSI resulted in the best gas mileage. It is less than the maximum for the goodyear tires (44 PSI). YMMV.

Note that I initially read 40 PSI using a standard (cheap) tire gauge. When I got a digital tire gauge it read 5 PSI lower. Since adjusting tire pressure to 40PSI I suspect that it will make up for my using air conditioning, maintaining my 30 MPG average.

When I take take my first long trip (PA to FL) in July, I expect 30 MPG highway, above the 27 MPG EPA estimate. This will be despite a loaded car on the way down, but empty on the way back.

Isn't this fun?