Use exactly what is recommended by Lexus as listed in your owners manual.
The 2008 Lexus IS-F's engine produces 416 hp @ 6600 rpm.
The 2008 Lexus IS-350's engine produces 306 hp @ 6400 rpm.
The 2008 Lexus IS-250's engine produces 204 hp @ 6400 rpm.
The 2008 Lexus GS-450H's engine produces 340 hp @ 6400 rpm.
The 2008 Lexus RX-350's engine produces 270 hp @ 6200 rpm.
The 2008 Lexus GS-350's engine produces 303 hp @ 6200 rpm.
The 2008 Lexus LS-460's engine produces 380 hp @ 6400 rpm.
The 2008 Lexus LX-570's engine produces 383 hp @ 5600 rpm.
The 2008 Lexus LS-600H-L's engine produces 438 hp @ 6400 rpm.
I have a 2008 ES350 that has had the oil changed twice. The receipt shows 8 quarts which in my opinion is a lot for that engine. -------------------------------------------------------- From the owner's manual for a 2007 Lexus ES350, it is 6.0 qts (5.7 L) without a filter and 6.4 qts (6.1 L) with the filter. Uses 5W30 oil.
The 2008 Lexus IS-350 has a V6 engine.