Light engine rattle at low battery (diesel engine sound almost)

Hey guys,

2013 Prius with 120k.

I've been reading around on this forum and elsewhere about this light ticking sound I hear from my engine. Think of a diesel engine. But it's not loud at all. It's not something that scares me or makes me feel like I'm going to break down or something. But it made me question.

I cleaned my egr/intake manifold about 10k miles ago (110k miles) and just recently changed to the updated plugs that Toyota switched to like a couple weeks ago. But the tick existed before that.

I notice it mostly happens when the hybrid battery is low (at 2 bars). But when it's at a good level it goes away.

I've read that it's the injectors doing their cleaning cycle? I've also read that my injectors could be dirty.

As for fuel economy, my car does good here. I'm getting about 58.4 mpg city.

What do you guys know about this? What could be a solution here? I've thought about putting some amsoil or techron with 93 octane fuel in it but haven't done it yet.

Before it gets asked, when I accelerate, the tick accelerates too. But like I said, it's not loud. I just hear everything lol

 

Yeah I did.

 

Hey mendel I know you're on this forum a lot.

In case you run into this question again this is what solved it for me. I'll explain what I tried that didn't work too:

Things I tried that didn't work. Each cleaner I used was as directed. So 1x bottle for a tank of gas. I did everything in this order

1. Replaced plugs with updated hotter spark plugs - no effect on ticking, increased mpg though and noticably more power.
2. 3x tanks of 93 octane fuel.
3. Techron, two times as directed. - no effect
4. Gumout all in one fuel cleaner. No effect.
5. Lucas fuel system cleaner. No effect
6. Highway driving for an hour, no effect.

Things that actually helped.

1. This was a minor thing, but I did notice the noise lessen here a little bit. I used Restore - Engine restore - 4 cylinder formula. Engine felt smoother, and this could be placebo effect but I felt like I had some power restored. 125k miles on my Prius. This product claims to restore compression and I've used it in the past with success so I figured I'd try it. Project farm on YT also tested it, and it does help here.
2. This is the thing that made the biggest impact. Marvels mystery oil, 4 oz in the gas tank in 10 gallons of 89 octane fuel (as per label). I used 89 because I remember reading that putting oil in your fuel tank, can lower the octane a bit. Not sure how true that is but that's why I did that. After about 70 miles of driving I noticed my engine felt significantly smoother, the tick is non existent now. 37 degrees Fahrenheit for whatever that's worth.

 

Also for the record, my oil does not burn, my coolant levels are perfect, all is good on that front. I check it frequently and my levels 4400 miles after my last oil change are still full.