2003 Prius, 47F, 9 miles, 51.3 MPG indicated

I needed to get some groceries early this morning, 4:00 AM, and walk the dogs. Before starting the engine, I cleared the "B" trip meter and reset the MPG display and drove to the all night grocery store about 4.5 miles away:

• 45-50F - temperature range spot checked on the drive down and back. The highest was in the parking at the grocery store.
• 9.0 miles, corrected to 9.5 - last summer, my GPS calibration constant came in at ~5.7% so I use 5% to be conservative
• 51.3 MPG, corrected to 53.8 MPG real - I'm using over-sized front tires, which is a permanent over-drive

Now I've been driving this 2003 Prius since October 2005 and do drive using a few tricks:

1. split water-noodle lower grill block - when outside temperatures are under 75F, this lets the car warm-up sooner to reach hybrid operating mode.
2. shift to "N" and 25 mph for the first mile - easy to do with no traffic, I only accelerate to 25 mph and then coast in "N" as much as possible.
3. keep engine rpm under 2,400 rpm - I have instrumentation that allows me to monitor engine coolant temperature and engine rpm
4. route that minimizes stops - this is specific to where I live but I can at 4:00 AM ignore one stop sign and use right-turn-on-red at the other intersections. With this cool weather, I'm at 70C within about 2 miles.
5. use the 40 mph access road instead of the 50 mph divided, limited access road - the Prius hybrid mode limit is 42 mph. So my indicated 38 mph is 40 mph true and the car loves to turn off the engine at every chance. This really boosts the MPG. But at 4:00 AM with little traffic around, I can also drive at 38-40 mph indicated on the 50 mph road without a problem by paying attention to traffic in my rear view mirror.
6. flat route - it is former river bottom land
7. heat only as needed to keep windshield fog free . . . heck I used defrost during the initial half-mile due to the condensate but I'm still coasting in "N".
8. I don't look at traction battery SOC but typically I arrive home with a fair SOC. I'll be doing 50 mph down to the turn into the neighborhood. Then I'm at 25 mph to the house so I'm probably parking with a little on the plus side of 60% but I really don't bother with traction battery SOC because it is just part of the transmission. I've long since given up on trying to treat our Prius as if they are some sort of electric vehicle.

The only reason I'm posting this is to list some of the tricks us oldsters use to squeeze our gas nickels as hard as possible. Add traffic, a poor route, higher speeds, and more heater, especially defrost that uses the AC, and the mileage would not have been so good. But I live in a milder climate and can use these Southern tricks.

No, I don't use 'pulse and glide' unless coasting in "N" called that during the first mile or so during warm-up. I'm only using coasting in "N" in the neighborhood when there is no traffic and only to get the engine coolant up to 40-70C depending upon how anal I'm being about mileage.

GOOD LUCK!
Bob Wilson

 

Even though I've still got a bunch of 88C thermostats for the NHW11, I've never put one in our 2003. I'm more concerned about the effects of heat on the engine and lubricants.

As for the 1.8L Prius, it does have an electric water pump. I am still curious why it has a thermostat versus using temperature sensors to adjust the electric water pump speed. That would take out the thermostat drag, lower pump speed and load, and during hot weather, help dump the excess heat after stopping.

Bob Wilson