Long Highway MPG drops less than 40.

The battery dropping to two bars and force charging back to full is a negative recalibration. It is the first sign of the battery degrading to the point of failure. If you recondition the battery now, the odds are high that you can extend its life a few years or more without having to replace any modules. If you keep driving until it fails with a red triangle, those odds decrease significantly. In case it helps, you can read about how to recondition the battery without removing it from the car here:
Battery Reconditioning - Hybrid Automotive

 

could be a lot of things. do you have it serviced regularly at a toyota dealer?

 

What do you think was the average MPH as a guesstimate?

 

Sounds normal to me. Of course, a routine tune-up is always a good plan anyway.

In heavy traffic, both my 2004 and 2010 would do the same thing. If you see it more often than just when getting stuck dealing with slow & waiting, that's different. Eventually, the battery-pack won't hold a charge as well.

I just took a quick long-weekend round-trip that was over 1,600 miles (with my 2012 PHV, no plugging opportunities). In the winter cold (sub-freezing) at extremely high speeds (mostly 80 mph), seeing 40 MPG was the expectation. That's normal under those conditions.

 

How cold was it on your road trip?

 

seems OK, highway driving uses more gas with the heat or ac is on and the battery will drain quickly in stop and go traffic..an older 12 volt battery will cause lower mpg because it needs to be recharged constantly

 

MPG goes down as speed increases, so at 70MPH that really doesn't sound all that bad. Other factors like headwinds (or even crosswinds) and variations in the gas formulation can drop you a few more MPG, so I wouldn't worry too much about it if your regular route MPG returns to near 50 after a while.

In a low speed crawl with very little accelerator input and the engine off, the Prius will often drop to about 3 bars before kicking the engine back on. So yeah you might get a little undershoot to 2 bars without it necessarily meaning anything too dire. The reality is that at 160k miles your battery is probably degraded to some extent. TBH that would be normal, but it doesn't necessarily mean that it's about to fail.

 

A lot of good advice has been given you may want to follow up on.

At 160K as service items you may want to see if the spark plugs have been changed, Throttle body cleaned, PCV checked,trans fluid changed, HV Fan cleaned, cabin filter replaced, MAF cleaned, HV Battery checked with Techstream Mini VCI, etc, etc etc.

Have some DIY fun.

 

I'll second what cc and others said above.
.
This Winter I did a cross country on I-70 and averaged 30 mpg doing mostly 65-70 mph for keeping up with traffic.
Also used cheapest gas. I suspect that ethanol was more that 10% on some fill ups based on how the car ran until after the next gas stop. . . . Used the heater and defroster most of the time cause it was freezin cold.

After that trip I did alot of what's noted above. Also switched from cheap, no-name gas to top tier brands. . . . Now 40+ on mostly short trips around the metro area and 50++ on the road.

 

Interesting results of you Prius.

I have a 2004 and runs great, 176,000 + miles on it.

Last year it went int to a "Grand Funk" of low fuel mileage. I hypermiled as much a I could to keep it above 50 mpg.
I was mostly successful with this. What I did find out on a long trip to California was it helps to drive the Prius hard, as I drove generally 5 mph higher than the posted limit.

The mpg started to increase and came back to an "easy" 50 mpg by the time I came back home. Easy means that I would see 60 mpg, maybe even higher, on a drive not hypermiling but not accelerating.

The "Grand Funk" was poor mileage in general. I do not know why though. I am glad the Prius decided to get better mileage.

Since many western states have speed limits of 75 mph and everyone does 80, I found that the Prius really likes high speed, getting better mileage on the MFD than at 70 mph. You can really fly over hills too since I noticed that going east out of Albuquerque I went over a crest at 91 mph! Ah! Gotta slow down the old Prius. LOL

 

I've actuallyQUOTE="CrazyLee, post: 2321457, member: 125912"]Interesting results of you Prius.

I have a 2004 and runs great, 176,000 + miles on it.

Last year it went int to a "Grand Funk" of low fuel mileage. I hypermiled as much a I could to keep it above 50 mpg.
I was mostly successful with this. What I did find out on a long trip to California was it helps to drive the Prius hard, as I drove generally 5 mph higher than the posted limit.

The mpg started to increase and came back to an "easy" 50 mpg by the time I came back home. Easy means that I would see 60 mpg, maybe even higher, on a drive not hypermiling but not accelerating.

The "Grand Funk" was poor mileage in general. I do not know why though. I am glad the Prius decided to get better mileage.

Since many western states have speed limits of 75 mph and everyone does 80, I found that the Prius really likes high speed, getting better mileage on the MFD than at 70 mph. You can really fly over hills too since I noticed that going east out of Albuquerque I went over a crest at 91 mph! Ah! Gotta slow down the old Prius. LOL[/QUOTE]
I've actually noticed the same thing with my 2005. High speeds and no cruise control, and you can actually get some good mpg numbers from the old girl. Although I try to keep it a smooth 72 most of the time just because I feel it isn't very good for the engine to be racing all the time.. Even with good mpg numbers!

Plus at high speeds my car uses more oil. So the less I speed the less I have to add oil.

 

The Grand Funk continues.
My mileage around town is now at a low of 34 mpg! The display showed 34.2 agreeing with my Dash Dyno fuel mileage display. Fuelly said it was 29.2 mpg! That bums me out. LOL

Last week the 12 V battery went bad, 10.67 volts (1 year old Exide at that!) , I was getting a dead battery on very cold nights. And since I saved my old Toyota battery I installed it, It showed 12.65 volts, and I had it it on a float charger.

I could warrantee it, but that means shipping charged on a 38 pound battery. I have gone on another route.

I bought a float charger that also de-sulfates.


BatteryMINDer Plus Charger/Maintainer/Desulfator - 1.3 Amp, 12 Volt, Model# 12117
In Stock Online. $19.99 Shipping
Northern Tool + Equipment Northerntool.com
2800 Southcross Drive West
Burnsville, MN 55306
Sales: 1-800-221-0516

I am leaving it on for 2 weeks in the garage and then swap the batteries. I hope that works.
Then I'll wire the charger to the battery and plug it in in the evenings. I can then say I have a plug in Prius !!!

I'll tell how it works in a few months.

 

Guess this is just on my mind today:

Another possible cause of low mpg might be engine coolant thermostat. They're a mechanical item, with a rubber gasket that can get brittle, crack, flake off. And they're opening mechanism can deteriorate, so that they're opening too soon, staying open too long. Between that and the failing gasket, it leads to engine chronically running cool, inefficient.

Any car with a few years and over 150K miles, it wouldn't hurt to put in a new one, just see what it does. Examine the gasket on the old one, and suspend both in a pot of water with thermometer, bring to a boil, to see how their opening varies.

This attachment is for 3rd gen, but it might be similar enough to help. Has some spec's:

 

Good tip on the engine coolant thermostat. You could use a Mini VCI and laptop to check the temperature. My Dash Dyno SPD fuel mileage meter will also read the engine temperature with a button press. I will check this out the next time I head on out.