2009 Prius - getting 28 MPG

I was wrong, you are never going to get 'normal' MPGs for a Prius as you do not drive normally. Constant acceleration is going to be much worse than cruising. Until you get the hang of it, you are probably using the friction brakes, rather than coasting to a stop and using regeneration.

28 MPG in winter is perhaps 3 times what a 'normal' car gets on your route.

You may never get over 38 MPG in summer when delivering mail.

 

Correct. And they will go back up when the weather gets warmer.

 

The 12V battery is very small in the Prius and still used just as much as any other car. If it is running low in capacity then it will constantly demand energy from the main traction battery. Check out these two threads:
10 mpg loss --->SOLVED! | PriusChat
Remarkable MPG increase after 12v battery | PriusChat

You can test the capacity by following this: Toyota Prius: How to Check the 12v Auxiliary Battery Health - PriusDIY.com

 

Some, but certainly not all, of the failure modes of the 12 volt battery cause it to have a maximum voltage of 10 volts. (shorted cell) While the Prius can start with 10 volts, the charging circuit will be 100% recharging it from the HV battery whenever you are in Ready. This constant drain has to be made up some where, so the engine runs longer.

The Gen 2 has a secret screen to see the 12 volt output before starting. Some morning before you put it in Ready, check it out.
Once it is in Ready it should climb to about 13.8 volts or higher.

Entering Maintenance Mode (aka 12V Battery Check) without Switching Headlights ON/OFF | PriusChat

 

What was the year/make/model on your previous non hybrid? Was it hand calculated?

Weather is a factor, as is driving route. There's another discussion about how cold winter weather can hurt mpg here.

You mentioned getting 44 mpg on a leg of a long trip. Track the mpg on a long highway round trip on cruise control and see if it's in the 40's. If so, you could be ok.

 

I have a very short "deal breaker" list, basically lack of spare tire. I'm gonna add touch-screens, as opposed to conventional knobs/sliders. That probably means I haven't got a hope-in-hell of finding a suitable new car, oh well.

 

Your 18-20 mpg would have been on the very low end for the 2nd gen xB's here. But that's to be expected based on your driving conditions.

I would have expected that a hybrid would have greatly improved your mpg. But if it's mostly stop and go, like a typical paper route, then the traction battery has little chance to recharge through braking.

Again, take an hour long highway trip using cruise control (round trip) after the engine has warmed up. If the mpg is low, then I'd dig further. Others here can advise you how to test the health of your traction battery.

 

Mine was doing same thing. Changed my plugs, its back to normal.


iPhone ?

 

Stop and go driving, delivering papers in the winter with the window down trying to keep warm causing the engine to run all the time..

I can't think of a situation that would be worse for gas mileage. I'm assuming the roads are steep also.

 

Also how are you tracking your mileage? Tracking it by hand with a fuel bladder in cold weather can’t be very reliable either. It’s much more accurate to just use the mfd.

 

Regardless of wild variations in "fullness" due to the bladder tank, any innacuracies will cancel out if you average two or three tanks. It inherently gets ever more accurate with every tank.

 

Hi Stephen. At this point I think you checked most things, so the most important thing you need to look at now is does the engine ever cut out (full EV mode) on your route? If it doesn't then you are unlikely to get much better mpg than any regular car of similar size.

One thing that is pertinent to the above and which has not yet been mentioned is the issue of getting your Prius into the mythical "stage 4" (mode of hybrid operation) during your route. Take the time to have a good read of this: http://www.techno-fandom.org/~hobbit/cars/five-stages.txt

The bottom line summary is that you wont get full hybrid EV operation unless you:

1. Get the engine up to full operating temperature, -AND- then
2. Either reach speeds of greater than 34 MPH -OR- stop and allow the engine to idle until it cuts out!

Yes it's a fussy little thing the gen 2 hybrid system, but those things really are required to get full hybrid EV operation. In particular the stopping (after the engine is fully up to temperature) and allowing it to idle until it cuts out, is the best way to make it "work properly".

Of course in your case the demand for cabin heat might screw you in this regard anyway (as it might cause the engine to continue to run regardless of taking the above steps). In any case, all you can do is try. If you can get the engine to shut off during parts of your route then you can probably improve you MPG, if not then I hate to say it, but you may as well have a regular car.

One final thing that might help you is choice of exactly how you traverse your given route. If it's possible to arrange it so that you do more uphill parts near the start and more downhill parts after the engine has fully warmed then you might be able to get substantially greater "glide" times (full EV operation without engine running). But remember that reaching "stage 4" hybrid operation is going to be important here, so you are going to have to jump through those hoops as described above.

 

Are all the addresses on your route spread out, or are there some clusters? Just thinking: would it be practical to drive only between the clusters, then park and go around each cluster on foot, reduce the stop-and-go factor?

 

you might want to keep the heat down and use the regular A/C for defrost. One thing that applies to all vehicles is that when you use the heater on a cold engine, you'll keep the engine cold for too long as it will be fighting to gain enough heat to reach optimal operating temperature. So keep the heat off until the car is warmed up. I don't know how cold it has been there for you but you might consider a grille block to help retain more heat in the engine bay for the winter time.

http://300mpg.org/wp-content/uploads/2012/11/DSC_4129.jpg

It's also possible your hybrid battery is getting weak and is on its way out, you just don't have a check engine code for it. Those low MPG are kinda borderline normal for the temps you're experiencing and driving conditions but you'll definitely want to keep an eye on the battery.