2009 Prius Poor city MPG

Hi Proverman. That seems kind of right, that the engine kicks in if you try to accelerate, but normally you should be able to accelerate past 7MPH in full electric mode if you do it gently enough (BTW, this is not recommended for fuel efficiency however).

What would be more interesting for us to know is, if you accelerate using the (gas) engine, say up to about 35 to 40 MPH, does the engine cut out if you then release the gas pedal? And if it does cut out, can you then keep the car running on only electric power for some distance, say about 1/4 mile if the battery was at 6 blue bars to start with? (test on dead flat road with minimal other traffic so you don't have to brake or accelerate).

Notes.
1. You need to be really gentle on the pedal to keep the car in electric mode like this.

2. I'm not actually recommending that you drive like this (on electric power) for fuel economy. I'm just suggesting it as a test for the health of the traction battery and electric drive system.

3. When testing stuff like this, keep an eye on the 6 bar (purple/blue/green) state of charge display in the battery icon of the energy monitor display. Report any anomalous behavior such as rapid swings in either direction.

 

http://priuschat.com/forums/gen-ii-...-answer-these-questions-esp-if-youre-new.html

 

Proverman, have you checked the voltage of the 12V battery? If the battery is weak the ICE will run more to try to charge it up. You can put the MFD in Maintenance Mode if need be to read the voltages.

To me, your original post infers everything is at operating temperature. I don't know what your driving cycle is so here are a few examples:

The 1st 5 minutes expect 25mpg as the ICE runs to heat the cat & itself. At a stop it doesn't shut off. Around 150F it is warm enough to start acting "normal". Operating temp is very high 180's to low 190's.

With a full battery the car has wonderful fuel economy in the city. The radio & the AC will discharge the battery faster. Once the battery is down to 2 bars the ICE will run just to charge the battery.

This week I simulated city driving at AAA Driving School. The car was on for a good 5 hours probably. Lots of standing. Hard acceleration. Hard braking. Speed under 30mph. The Trip B odo showed average speed of 3mph and fuel economy in the low 20's. The day's driving probably knocked 1-2mpg off the tank average but overall this was still an above average tank.

On my 2006 the original battery lasted 3 1/4 years. The replacement OEM battery from the dealer lasted 6 weeks & was replaced under warranty. When the battery fails the symptoms are that the SKS doesn't work, the interior lights don't come on & the car won't start. If you try 3 times it may start. If so, drive straight to the dealer or be prepared to jump it.

I'd also check the oil level. Too much oil will hurt FE. Way too much will get the car towed off the highway.

Check the tire pressure. Higher is better for fuel economy & handling.

 

I would say it is not correct, though my Prius is a later generation than yours.

The speed at which my ICE starts is highly dependent on conditions. On very gentle takeoffs I can get it up past 25 before the ICE starts, though this is very bad for fuel economy. When taking off fast or uphill, the ICE can start immediately. I normally don't track this, but expect a typical value to 5 to 10.

I would suggest not trying to game this issue for a while, just drive the car 'naturally' without trying for fuel efficiency, in order to get a baseline. After that, then start trying to push up the performance. If you were complaining to the dealer just 3 days after purchase, there was a significant chance of overthinking it before learning the car.

Otherwise, please fill out Cwerdna's questionnaire. That will draw out a lot more information to help us try to figure what is happening.

 

My two cents worth. I think the clue is you get better mileage with the ICE running (highyay mileage). Don't try to run on battery alone. Get it up to the city speed limit briskly then let off the gas slightly and maintain your speed. Watch the consumption screen for mpg and let the Prius keep track of battery charge. The Prius very efficient when the ICE and electric motors work together.