Tips to revitalize a slowly-decreasing mpg 2006? (160K miles)

The mxv4's are still quite a good LRR tire though. I'm not sure exactly what difference 195/60/15 makes in comparison to 185/65/15, but here in Australia (and on several other overseas models) the 195/60 is the stock OEM size. I think it probably doesn't effect fuel economy by much more than about a percent or so. I still get 55MPG running that size.

Yeah that's right, the blower only operates from 12V and the AC compressor runs from the high voltage bus.

It's interesting about the thermos coolant pump apparently not running. We don't have the thermos on the Australian model so I don't know much about it, but it does seem like a sign that your battery has been very weak for some time. Anyway, I hope the new battery improves your mpg and will be very interested to see the results after you've done some more driving.

The thing about the Prius 12V battery (usage) that is so different from a conventional car is the fact that it doesn't need to crank the engine (the traction battery does that via MG1). So whereas in a normal car a weak battery quickly becomes apparent when cranking becomes sluggish, on the Prius the battery can just slowly slide away to oblivion without anyone noticing.

 

When you first turn on the car, roll the window halfway down, then roll it all the way up, and hold the switch in the up position for 2 seconds.

 

Your battery with those numbers is toast. And the mileage numbers your claiming are a miracle.

 

Might be time to replace... I'll double-check again and probably will replace if it goes any lower. On our Camry I've only replaced the 12V twice in 12 years/150K miles (once every 6 years). Perhaps the Prius smaller 12v battery does not last as long? Are there any observations as to how long the average Prius 12v lasts?

As for the mileage, the MID is showing b/w 47 and 48 for my first 300 miles on the car since we got it and is pretty stable there. That's mostly city trips under 10 miles with the carstarting from cold in the morning and in the evening, so that brings things down a bit. When I drive it climbs-up towards 48, when my wife gets it, it goes down toward 47 but has not fallen below that, yet Just filled-in my first tank and the actual was a bit over 43mpg, but with that bladder I'm not sure how accurate that is (even though I used the same pump where I fueled my first full tank before that).

 

Checked this morning again so I could get the numbers right (after the car has sat overnight without driving it). After hitting "power" once, the voltage was 12.1 with no load and 11.8 to 11.7 when I hit the power button for a second time. When I press the brake and hit the power button a third time (to start the car) the voltage goes to 14.1

These don't look too bad, I guess. Will wait to see if they go down over time before I replace the 12v battery...

 

Yeah kocho that's getting marginal, but not completely gone. I've got a battery in similar condition that I'm keeping my eye on, I know I'll have to replace it soon though.

Batteries in that sort of condition are obviously not good, but they don't always cause the sort of power drain that will hurt the fuel economy. Sometimes they just get reduced capacity and higher resistance (both of which are bad in the sense that it makes it more likely to leave you stranded) but they don't necessarily cause bad fuel economy.

You could try putting it on a slow charger overnight and see if it help. Chances are however that (like me) you'll still need to change it in the not too distant future.

 

i think i now wy your AC is working better
maybe the failing 12 volt battery was using a lot of amps from the dc-dc converter where the 12 volt ac FAN is also running from.
maybe thats wy the fan was running so slow and now is getting more amps because nothing is lost in charging the 12 volt battery