l just bought a 2009 Lexus IS and had my first gas tank fill up.l put regular fuel in but should l be using a better grade?If so do what grade do you suggest?l checked out the book, l am sure it is in there but l must be missing it.Best Wishes.
It is a Lesus IS 250 All Wheel Drive
Sorry Lexus is spelled wrong above.

the owners manual should have a recommended octane to fuel your car. Mine is 91 but l usually put in 87. Now if your engine ''requires'' a high octane, definitely go with that.

The only difference you will notice is power output. Lexus engines are designed to run optimally with higher grade fuel. l would suggest using 91 octane as a minimum for high power output and fuel economy. You wo not hurt anything by using a lower grade fuel but will lose 5-7% horsepower and fuel economy.

Since gas is so cheap right now l would suggest 91, but if gas goes back up l would put mid-grade so that you wont lose too much performance.