Regular or high octane?

When was its last good tune up? There could be something else going on as you normally won’t hear anything unless you got really poor quality fuel. But if you want try a few tanks of higher octane and see if it goes away, it not going to hurt anything.

All Avalon engines were designed to run on 87 Octane or higher. But as engines age, that can change. With engine wear, you lose compression, not a lot in a properly maintained engine, but you lose some. And then there are failures of engine components, like sensors. If I heard spark knock in an engine, and that might not be what you're actually hearing, have a mechanic diagnose it. He might find that you have a defective knock sensor, or something else that needs to be fixed. And any repairs that are needed are necessary to do. There are no advantages to running Octane higher than 87 in your car except to quell spark knock, if done, it should be a temporary measure until you can get the underlying problem repaired.

Thank you very much, for detailed answer. Have a nice day.

I agree, sounds like a bad knock sensor. If your check engine light is on visit your local auto parts store and have them scan the computer for trouble codes. Most stores will do it for free. If you get a knock sensor code, there you go. Hope that helps! Jim

Thanks ,for your help

You're welcome. Glad to help! Jim