Looking to buy.
Worried about the 4 cylinder turbo-charged engine. Should I be?

then go for the 350h hybrid. No turbo.

I want the leather interior, though.
Also worried about "hybrid" related failures.
Have there been issues with the RX 4 cylinder turbo-charged similar to the Honda Accord 10th gen?

Other than some software updates requiring reprograming of the ECM, I am not aware of any issues with 4 cylinder turbo engine. It was first introduced in 2021 and its use has since expanded to a few models across the Lexus/Toyota line. Long term reliability is yet to be determined, of course, but so far so good IMHO. While the engine is noisy at lower speeds and fast excelleration, I have gotten used to it. At highway speeds it is quiet, smooth, and has plenty of power when you ask for it. I like the fact that it has dual injection- port and direct, which should mean less intake soot buildup. Most, if not all, of the other small turbo 4 bangers that I am aware of are only di.

If you are into such things, there is some good information on the engine found here.

The 350h Premium + and Luxury trims come with genuine leather seating surfaces. Read up on Toyota hybrids. They are highly reliable.

I bought a 2025 350h P+ in January. I avoid anything with a turbo since they usually require premium gas (which the RX350 turbo does) and the extra compression adds wear and tear to the engine. Toyotas 4th gen hybrid system, like the one in the RX350h, has been around since 2017 in the Toyota RAV4. Hybrids rate as the most reliable engine choice; over ICE engines. My other hybrid (2019 Highlander) has been a workhorse with no isses beyond the fuel pump recall.

As for the 2025 RX350h. I can only compare it to my sons 2017 RX350. The new vehicle is smoother and quieter; but some materials feel cheaper. Namely the steering wheel and the leather seats. Everytime I drive it, I miss the luxurious feel of the wood steering wheel on the 2017. The new one feels like plastic and the leather is low grade. The steering wheel on my Highlander feels very soft and premium; not the 2025. The seats in the RX are also not as comfortable on trips. I'm only 5'7" and 175 pounds, but it's too firm for my liking. Maybe they will loosen up over time.

Power delivery is good and I have never felt it needed more. I've read/watched just about every article/video review and performance numbers are almost the same. I don't see an advantage for the turbo, other than a discounted price. The eCVT is super smooth with no hesitation. However, you can hear it hold gears during spirited driving. I run regular gas and consistently get 41+ mpg in the city. And the vehicle only has 1,000 miles on the odometer, so it should get better over time. Keep in mind, driving a hybrid is different. My wife averages 36 mpg since she drives it like a non-hybrid and has a little highway driving mixed in. She also drives faster and more abruptly. If you want better gas mileage, you need to have a lighter foot. Granted, even with my mpg numbers, I'm still the first one off the line, but I relax my driving once up to speed.

Bottom line; test drive both non-hybrid and the hybrid. You'll see why the non-hybrids are discounted and on the lot and hybrids are bought for MSRP and before arriving to the dealerships.

If you buy the turbo you'll have to do oil changes at least every 5000 miles and use premium gas in hopes to not have issues.

The naturally aspirated Hybrid has much less maintenance, regular gas and good track record for reliability. Transmission also has better reliability record.

I simply do not trust mass-produced turbos to last. So I bought a hybrid. It's a '23 Premium+ with leather. Perhaps the current production lacks leather?

ALL Premium Plus has real leather seats.

The 2025 Toyota Crown Signia Limited Hybrid is starting to look good to me after watching this video:

KBB.com High Fair Price is $49,133 for the Signia Limited Hybrid vs $57,927 for the RX350h Premium+.
Both have the hybrid engines, AWD, leather seats, and 21 inch wheels.

I've driven both. Bought the RX350h for the improved cabin materials, insulation, ride quality and interior room. Also, my sons are too tall and wouldn't fit in the back of the Signia. Wife and I are small people and we felt the front was too confined (narrow) for our tastes. Drive them both and see what feels best to you.

Have you considered the Lexus NX? I think it's a better comparison to the Signia.

Yep Signia is to Highlander as NX is to RX. I teat drove an NX before buying the RX. It was a non starter front seat space wise and also a bit noisier than the RX. It's actually my wife's daily driver and I was eager to save about $10k but she wouldn't have any part of it after driving an RX for the last seven years.

Interesting to know. I would've waited to test-drive the Signia, if only they offered the Plug-in version in the US (they do elsewhere apparently).

Nonetheless, what was your driving experience difference between the NX and Signia, assuming you test-drove both ?

The Crown is a rather confused branding/product by Toyota, since its literally seems like a Toyota+ - which is what Lexus (NX) is.

Then you're the only person that thinks this. The 4 cylinder doesn't hold a candle to the old V6 for smoothness and quietness.

You're kidding - the V6 in the last generation waz anything but quiet.