Two day drop in MPG after inverter coolant change?

i would ignore short term mpg and concentrate on calculated fill up tank averages.

 

If anything, the OP might have drained the 12 volt battery slightly. I doubt seriously he/she could damage the traction battery with IG-ON sequences as described.

Agree with Bisco. I would ignore the short term MPG and look at the BIG picture.

 

if your next couple tanks come in low, report back. anything is possible, but not everything is probable.

 

If you were to have "messed up" the inverter you would be getting the red triangle of death.

I would be willing to bet you simply drained down the voltage of the 12 volt which caused the ICE to work hard to recharge it. But that is speculation on my part. I do know the 12 volt is wimpy in the Prius and it does not take much to pull down the voltage. The reserve on that 12 volt auxiliary battery is rather low and it does take quite some time for the Prius to recharge it. Quite a few post's here on Prius Chat about MPG dropping before the 12 volt battery dies. Again, in my opinion I speculate you simply drained down the 12 volt causing the ICE to work overtime to recharge the 12 volt battery.

In reference to your inverter fluid change. As long as you see turbulence (good flow) in the reservoir when the Prius is in "Ready" mode, chances are you good to go. Also if the inverter pump is quiet and NOT making a lot of noise, chances are good that the bleeding procedure you should have done should be Ok. I would check for turbulence in the reservoir and confirm that the fluid level is full. If both of those items are good, chances are you did the drain, refill, bleed routine Ok.

 

You may air in the system if you did not properly bleed the air out after the change out. Its really easy to bleed the air out. But it must be done.

Get a flashlight and put the car in READY and open the hood and open the Inverter coolant reservoir and look into the tank and see how aggressive the coolant is pumping. Should be bubbling really hard in there. After a new change my coolant looks pretty torrential in there. Way more agressive with new coolant. Check all the fluids under the hood.

After any repair the Prius seems to go into a funk and shows poor mileage. Especially after a visit to the dealer. I susupect the 12 volt
battery is marginal like Ron said.. If you have a voltmeter first thing in the am before starting the car measure the front jump points. Post that number. I'm guessing 12.1 volts or worse. It's a really good idea to at least monthly throw a 12 volt charger on the car and charge the 12 up. Pay attention how long it takes to charge up as thats a really good indication of the battery health.

Same goes with the Hybrid Battery. I bought the Hybrid battery charger they sponsor here on this site from HybridAutomotive and every couple of weeks I charge the h battery up. Seeing good improvement there. At 150K miles that's right where the Hybrid battery really starts to show its age. I do both batterys at the same time.

Every once in a while I will baseline my car. Late at night find a nice straight level road for 4 miles no hills and put the car into cruise control and don't touch the gas for 4 miles. First clear the mpg indicator to 0 on the mfd. Get the car up to 60 miles an hour and engage the cc and clear the mpg meter. My car with the air on and lights and radio will do 58 mpg's at the end of that 4 miles. And thats with my tires at 35 lbs.

 

Now you know the root cause of your MPG drop.

Consider buying a modern smart 12V battery charger. 12 Battery Charger | PriusChat
Very useful tool. Use of this, after any discharge, or even as periodic maintenance, can't hurt. It will definitely eliminate a discharged 12V battery, as a contributing factor of low MPG.

 

I'll second that and add that a immediate charge after a significant discharge event will greatly add to the life of the battery.

 

Forgot to mention, you can always just connect the charger to the 12V battery to prevent it from being run down, if working on the car in ACC or IG-ON, for a prolonged period of time.

Another thing to quickly and easily rule out as a cause of low MPG, is tire pressure. If under inflated, it will kill MPG and wear the tires out faster.