Squeaking From Motor

Probably the idler bearing for your fan belt.

I've had two replaced in the past 95,000 miles.

The serpentine belts will get "glazed" and tend to squeak from time to time. When the bearings go it is usually a noise that is continuous. You will use the longer of the TWO belts listed for the W22 chassis with the 8.1L engine. Since you will need to replace the belt, it is not a bad idea to replace both the idler pulley AND the tensionor pulley. This is not a really difficult job to do but it does need to be done from the top for the idler pulley and from the bottom for the tensionor and belt change. I've change the belt at the side of the road. Takes about 15 minutes to do. I would get a Gates belt instead of the cheaper Dayco belt. It will last longer.

Try with the engine off and cold dump a bunch of water over the belts. Then start the engine and see if the squeak is different or gone. If no change then look at the bearings.

I looked at Advance online and they listed an Idler/Tensioner Pulley. Are there two? And if so are they different? The game is afoot as Sherlock says! Thx.

Two different parts.

The idler is a fixed pulley at the top. The tensionor pullet is on a spring loaded bracket that you have to release to change the belt. As the name indicates, it keeps the tension on the belt. You use a 3/8" breaker bar in the tensionor bracket to release tension on the belt.

Just a personal observation. I have always considered belts as squealing. A squeal lasting more that a squeak (which is more of an instant)
Have had springs squeak, motor mounts squeak. Brakes and belts squeal.
The word squeak seems like something that happens very quickly

I agree. The sound is more like a chirp, chirp. Doesn’t squeal like a slipping belt.

The chirping sound occurs when your alternator kicks on and off, which causes additional drag on the belt. Alternators are not charging at their full capacity unless needed. When they start charging, the drag increases, which can cause a chirping sound. When you initially start your engine, it takes a lot from the batteries and they need to be topped off, hence the alternator kicks in. If you want to dig around underneath and on top of your engine, you can buy a can of belt dressing and thoroughly spray the belt all over and let it dry. Then start your engine and see if the noise goes away. Belt dressing is not a fix, but in some cases it does quiet a slipping belt for a short time.

A quick and easy check for belt squeak is to spray each individual belt with a squirt of water from a spray bottle. If the squeaking belt gets a shot of water it'll stop squeaking right away and probably start again real quick.