ICE on or off in traffic?

Just drive it. I let my RADAR cruise just drive according how the traffic is flowing.

Gentle-moderate acceleration where it's not holding traffic up, predicting traffic lights, keeping a good distance behind the car in front - and lots of other techniques can help with economy.

IF YOU REALLY wanted to do a test and maybe squeeze a little more out of every litre, you could STOP and power off immediately before taking the route - that would reset your MPG display - and see what it is at the end, using a), b) and c) on successive journeys. Also assess which is the most/least frustrating. I'd suggest doing each of a,b and c at least 3 times, tabulate them and then analyse the results, as one day each could give false results (different wind direction, warmer/cooler, lively music on the radio, good/bad mood etc).

Trying to force EV mode hasn't seemed to make much difference to my economy - except in very limited circumstances. A hybrid is designed to use both in combination, and I think PRIUS's computer is more adept to it than I am - usually.

The exception is if you are intent on "hypermiling", but I have almost always found that traffic isn't generally suitable. If you want to read up about hypermiling, google "hypermiling prius". It's probably fun in its own way.

The ICE and it's lubricants are designed for the on/off cycle, so don't worry about that.

 

Consult 10 people, and you'll probably get 10 different answers.

I may be the only "non-typical" Prius driver in these forums. I've only had my Prius for nine months, but I discovered that I get the best gas mileage when I just drive it like a normal car. I rarely even keep track of when the gas engine is on, or when it's in battery only mode. (I can hear it, I don't need to look at the gauges.) I just let the hybrid system do what it's going to do... regardless of speed or traffic conditions... I don't try to overthink it or analyze it too much. (And I refill my tank when it gets down to 1/2; or 1/4 at the most. I don't drive it until dry.)

Would you believe I get the best gas mileage in the PWR drive mode? I also don't mind the gas engine going on and off as much as it wants to. I actually like to "exercise" it; keep it lubricated and running well. I don't want any seals drying out. (I wonder about the new Prime plug-in model. If you lived close to work, you could drive that thing for two weeks and never see the gas engine come on. Is that good for the engine to be non-active for so long?)

 

Just drive it. (Prius driver since 2009)
If you want do as post 2 says: try a b c and reset the Trip at the end of each drive and see what is best.
I noticed that when I try hard to save fuel, I don't (apart keeping speed down). When I don't do that and simply trying a smooth ride by predicting traffic, stops and traffic light, I get the best mpg.

 

When I got my 3 and then my 4 I had like 3-4 months of looking at the screens continuously to see what's happening. In the end I ended up with a setup that I like and look at the road instead the whole time (as one should!).

 

I keep the ENERGY MONITOR showing - it keeps passengers intrigued - even my 87yo Mother will comment on it from to time, and people who've never been in a PRIUS before are fascinated.

 

There's no problem with glancing at the screens - with the HUD, you've got probably the most useful directly in your field of vision.

The PWR gives a more "sporty" feel to the throttle - you need less movement for the desired effect, and yes, it's easier on the foot. I find that the RADAR cruise seems to work a bit better with PWR mode, keeps to the selected speed better.

 

Watch the ENERGY MONITOR - it'll show you that it flicks continually between about ½ dozen different drive patterns. As an example, it might REGEN for 5 seconds, EV for 7 seconds then back to ICE, then down a hill it might REGEN for 50 seconds then at the start of going up the next hill will use 10 seconds of EV then ICE up the hill.

It's part of being a HYBRID - it uses whichever mode is best at the time. Best way to look at it is that the PRIUS, rated at 50-56 US MPG compared with a roughly equivalent sized NON-HYBRID car, ie a Corolla at 30-34 US MPG. How PRIUS is rated for 55-65% better economy is by the savings of those short periods of REGEN and EV, interspersed with ICE.

Don't forget that time in (pure) REGEN is time the ICE isn't working either.

In my opinion, the computer is doing a good job generally - but as I said in an earlier post, if you REALLY have the patience to try HyperMiling, you can improve possibly a few more percent.

However, it's a case of diminishing returns. If you were driving a fuel gu$$ler Landcrui$er rated at 15MPG and improve by 5% by hypermiling, you'll save a discernible $$$ amount, but improving a 55MPG PRIUS by 5% - I'm not sure you'd really notice the difference - maybe $2 per fill at our much higher fuel prices in Australia.

 

Two thoughts to add to the above discussion:

1) Without pressing the EV button, the amount of electric power that is available before the ICE starts does vary with battery charge (in the Gen3 at least). At 6 battery bars, the ICE comes on later, turns off sooner, and doesn't charge the battery much when it does run. At under 4 bars, the ICE comes on very easily, stays on longer, and puts much more charge into the battery. Thus, in stop and go traffic you usually end up at some moderate charge level unless you do something extreme.

2) In my opinion, it's only possible to hold up traffic if there's nothing but empty road in front of you. When the car in front of me is doing 0-35-0-35-0 with hard accelerations and braking, I'll shoot for a steady 20 with gentle changes in speed as needed.

 

I think if you just drive it it WILL be "ICE on and off". If you're gentle on the accelerator it will be more off than on.

 

I'm embarrassed to say, that yes, I have become distracted quite a few times. And I had a few close calls because I was looking at those darn screens (or adjusting the radio) instead of keeping my eyes on traffic in front of me. (This is my first Prius).

That's another reason, that I never use my cell phone while driving. I don't have it programmed into the system, or the Entune, or anything. Maybe it's my age (62) but when I got distracted so easily, it scared me.
I almost rear-ended a few people. And ran a red light or two! The large center screen can be turned off easily. And the two smaller screens up on the dashboard I can change, so that only the compass is showing.

Watch out for old dudes in a Prius!

 

I have to agree with those suggesting just drive it. Only had my car just over a month, but already I've found the case is perfectly capable of doing exactly what it needs to do.

Sadly, I would beg to disagree with anyone suggesting to try comparing the three different styles of driving. That's because unless you are driving a huge distance, the many slight variations in the road condition, traffic, temperature, humidity and air pressure plus several more things would make it completely unreliable.

I would recommend allowing the ICE to warm up before using EV mode as the catalytic converter has to be warm enough to do is job well, but just drive it and stop worrying.

 

The Catalytic Converter warm-up (it gets mighty hot!!) will be part of why, once the ICE comes on, it runs for maybe 1km before shutting off. I can't see any reason for not using EV at cold - if you don't want the heater running. It could depend on your commute. My commute starts in a quiet street where it's not safe to do more than about 30km/hr - about 300 metres before I get to a slightly faster street - so I do that section usually using EV - it starts the ICE as I round the corner and the ICE is off again when I hit the main road.

 

Peace......

 

You cannot use EV when it is too cold. I tried yesterday after watching a Gen 2 leave in EV mode.

 

I suspect it'd be the heater which is telling your ICE to turn on - I got around that in my winter (which is relatively mild) by turning the temperature setting to minimum (I think 16 or 17C) when I parked the night before - that way it didn't usually start the ICE immediately - though sometimes, the PRIUS computer has a mind of it's own.

That said - it didn't make much difference to economy either way.

 

Like I said, I looked. It was colder than 68F (20C) outside when I tried after the car sat all day.