Does ECO mode hurt the engine in the long run?

No reason to be concerned. That has been part of the design since way back in 2012.

 

I found ECO hurt my leg: too dang much travel. Played with ECO for maybe the first 6 months of ownership, switched to "Normal", then never touched it again.

 

The 3 modes - Eco, Normal and Power are only changes the gas pedal sensitivity. In theory, you can get the same mpg and acceleration in all the settings. It is just easier to accelerate slower in Eco mode and easier accelerate faster in power mode. There is no computer magic other than that. I go with normal mode all the time.

 

on the gen 3, there is some concern that it might indirectly affect the headgasket, but it is one of many unproven theories.
in gen4, there haven't been any issues i recall reading about, and we're talking almost 6 years now.

 

I’ve found that if the engine starts to cool, it’ll kick on regardless of how charged your battery is n

 

that's true because of the pollution control laws, and dependent on the ambient temp. another concern is the kicking on and running to bring up temp without much load.

 

Cabin heat demands are another factor: especially when the car’s only partially warmed

 

It uses MG1 as a load to generate electricity for the battery during the warm up cycle. It isn't just idling to warm up the ICE.

 

I was beginning to be worried......that no Prius owner had come up with a new obsession to discuss here for a really LONG time.
Now we have one.

Simple answer: NO. It doesn't really cycle from HOT to COLD but from warm to warmer.

 

I'm pretty sure that there are a few other subtle changes too.
Like cruise control sensitivity and limiting aggressive cabin cooling.

I too did a little unscientific testing and never touched ECO again.

 

it has changed on gen4 from gen3

 

Just drive it - that's what it's designed for. It'll all last the life of the car. In many assessments, the most reliable car on the planet - driven that way.

I use ECO 99% of the time - and RADAR Cruise almost as much.

 

I leave mine in Normal mode all the time.

Like others, I messed with the other modes when I first got the car, but I find Eco too lethargic and Power too eager. Whichever mode you are in you can still get full power if needed by simply flooring the throttle.

You can use Normal mode, but put the air con in Eco mode if you prefer.

 

Nothing new to add. Just reinforcing what other have already pointed out.

I drive exclusively in ECO. Approaching 59k miles in a few days.

The car will not let the ICE cool off while driving once it's warmed up. (edit to add: If you are in HV. EV keeps it off indefinitely.)

If you watch the energy monitor, you'll see that, while the ICE is warming up at a stop, it is doing work by charging the traction battery.

Running in ECO, I would not expect my wife's Prius engine to last more than about 250k miles. My Prime's ICE will probably go to 500k if the rest of the car lives that long.

The Prius and the Prius Prime are among the 3-5 most dependable and long lasting cars ever made.

 

Full disclosure: I’ve heard 4th gen ECO mode is about the same as 3rd gen Normal; all the modes have been shifted.

 

Although Gen 3-specific, these hunkering experiments revealed some interesting bits of the control logic that depend on whether you are using the heater or not.

If you are not using the heater, the ECM sees no point in ever running the engine without bringing it to full operating temperature, around 90 ℃. Once it gets there, it cycles the engine as needed to keep it in an 80–90 ℃ range. So it is keeping the temperature swings to within ten kelvins.

What was interesting was that if you are using the heater (again, this is the Gen 3 coolant-derived heating, not the Prime's heat pump), and the ECU figures out that you are really just parked and using the heat, it drifts those control points downward until it ends up just keeping the engine cycling between 50–60 ℃. Still plenty hot enough to keep you cozy in the cabin, but just lukewarm in engine terms. And still only varying by ten kelvins across the cycle.

If there were any grounds for worry about thermal cycling, that might apply more to the imaginary "hunker-extender" device I proposed in that post, since that would be a way of lengthening the engine cycle so the temperature range would be wider than 10 K (though it would still only be the 'warm' 60 ℃ at the top).

 

Thanks, @ChapmanF for the clarification. Being down here I sometimes forget about cabin heat since I only use it a couple times per year. I should remember what it's like from my cold weather trips to Ohio in the PiP.

 

250k miles - I'd be dead bored with it - and 500k - eeek.

 

Yes, same here - maybe in June/July/August it'll be on.

But if the Climate Control is turned OFF in winter, you'll only get about 1 kilometer driving before the ICE starts - and then it runs till it's up to full operating temperature. And from there, it's on and off - it's never off long enough for it to cool appreciably before it needs to either drive you, or charge the Hybrid Battery.

Maybe if the OP were to put this (in the entertainment)

or this in the main display:


it might help him or her.