Is a high pitched whine normal in ES300h?
 

Just test drove a 2014 ES300h, and at highway speeds there was a very high pitched noise that never went away. It was faint and could be covered up with the a/c or music, but if everything else was off it was clearly audible.

Is this normal or just an issue with the specific car I drove?

Yes this is normal. This is MG1 which spins at high rpm. The ESh makes all sorts of weird noises when it starts up. It has an electric vacuum pump which powers up the brakes at startup. All normal.

This is at highway speeds though.

I can't recall ever hearing anything like that on my 2015 or 2019 ESh at highway speeds. It may be that your hearing is just better or more sensitive to higher frequencies than mine or my wife's? There is always a possibility that the MG1 is worn and has simply become louder with age. There are many members on here that have 100K miles or more and I don't recall them making this observation either. Now at lower speeds, where you aren't experiencing as much wind or road noise it is certainly possible - though I would think still unusual. Was this observation with your windows up or down? I rarely drive with the windows down so that may also explain why I never heard it?

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The newer generations of ES do not have power steering fluid...they are all electric.

Not normal. The wine is only audible during regen braking. Even when moving the car using the traction motor only (EV mode) the sound is faint especially with the windows up.

this behaviour is the same for all the Lexus and Toyota hybrids I drove or owned.