HI,
I just brought a brand new Lexus, in the manual it call for 91 octane gas. At gas station the premium is 93 and the mid grade is 89, can I fill the gas with 89 octane? Will it damage the car engine if I fill the octane lower than it recommend?

Liana.

Over time, it's not a good idea. A compromise is to alternate filling the tank with premium and mid-grade. Start with premium and refill it next time, at the half-mark, with mid-grade. Alternate back-and-forth. (93+89)/2 = 91.