Short trip tips?

Getting back on subject here...

The fuel gauge hit half full (half empty?) at almost exactly 200 miles. Fuel gauges are rarely linear though, anybody know off the top of their head how many gallons that would be? (Roughly, of course). Maybe I will just fill it up on the way out this morning, just to know.

Having watched the energy display for a week now it is evident that this car takes a very long time to reach normal operating temperature, at least on the route I'm driving. It never takes less than 10m for the car's mpg/ 5m display to reach the point where it stops rising.

My HCH1 warmed up faster, but it wouldn't shut off the motor at stops until it was at full operating temperature. So I could tell where that point was, and it was at about 5m. Coincidentally the car before that, a Mazda Protege5 also reached full operating temperature at the same stop light, which was evident because the idling RPM would fall suddenly when it shifted from open to closed loop.

If I had to guess the problem is all the stops. The motor shuts off at each and every one of them, even the very first light. So not only is it not warming up, given the tiny motor and exposed surfaces it is likely cooling off substantially at each stop. It also isn't heating up the catalytic converters very quickly. The HCH1 I used to drive had the same fast cooling problem, but it was only evident in the winter. When it came to a stop with the heat on the motor would shut down and the air coming out of the ducts would start cooling off. If the stop was long enough the temperature gauge would also fall. The Prius has no such gauges though, so the stock display isn't going to give up this information. The proper cable has been ordered, once that is in I will be able to monitor temperatures to see better what is going on.

I'm also wondering a little about the heat setting. It isn't set to auto, and the temp is 72F. There is no specific "heat/cool" switch and I wonder if maybe the car is drawing heat off the motor to warm the cabin which also contributes to the slow warm up. (It would do that at a stop even if the motor is off.)

 

Yes I dropped the "i", it was miles not meters.

Two new pieces of data.

Filled it up to find out what half a tank was in gallons. Of course pulling into the station it dropped one tick below half full.
208.8 mi at 5.4 gallon so only 38.7 mpg. The running mpg (reset at the beginning of that) was 39.5mpg. The display
was 2% optimistic or the odometer was off 2%. The dealer put on new tires (Bridgestone Ecopia), I need to check that they are the right size (which could easily shift things by 2%) but even if they are, they are also new, and Toyota may have calibrated things for tires with 50% wear (or something like that). Anyway, the display and actual mpg were pretty close. Looks like 5 gallons is a pretty good approximation for gas used to half full.

Measured the car's 12V battery voltage 5 hours after it was driven for 10 miles. This used the built in diagnostics to get to the "Vehicle Signal Check" page. That showed 12.1V. Pressed power button one more time to get to ACC (low fan running, no radio, no cabin lights) and it fell to 11.3 before rebounding to 11.7. That does not look like a good 12V to me, it looks like one which is about to die. Never mind that the dealer's million point checklist (you know the kind) showed a good 12V battery. No problems starting it yet though. Have not yet checked it right after turning the car off. Not sure yet if it isn't charging to full, if it cannot hold a charge, or if there is some left "on" in the car which is discharging it. No cabin lights on when the car is off. Is there anything else that might be turned on drawing power from the battery?

It occurs to me that if the 12V is really bad the car may be running its equivalent of an alternator (an inverter?) much more than usual, which could depress the mpg some.

 

Wait, that wasn't what I meant! "m" was minutes, not miles or meters. The point I was trying to make was that other cars I have owned reached stable operating conditions in about the same elapsed time of 5 minutes of warm up, but this Prius doesn't. I think because given the stop/go nature of the trip and the long times the engine is off it is only actively warming up half as much. For the other two cars that 5 minutes was about 1.4 miles. The Prius seems to need around 3 miles to warm up.
[/QUOTE]

Measured the voltages two more times for this table:

	time	V1	V2min	V2final
1	300	12.1	11.3	11.7
2	1260	12.1	11.2	11.6
3	3	12.4	11.7	11.8

time is in minutes since the car was turned off
V1 is the first diagnostic voltage
V2min is the lowest diagnostic voltage on entering ACC-ON mode,
this only lasts for a second
V2final is the stable diagnostic voltage in ACC-ON mode, after the voltage
stops fluctuating.

Last line is after driving ~7.5miles to work.

Pretty sure the battery voltage shouldn't be below 12 in ACC-ON mode. (Lowest fan setting, display on, nothing else explicitly on.)