Hi again all. Thanks so much to those who posted responses to my last question about VSC issues. This forum is VERY helpful. I've had my 2005 Prius for 8 months or so. When coasting, I noticed that my little mpg readout would always say 99 mpg. This has recently changed - within the last month or so. I'm wondering if this is normal? Now, when coasting, it takes about 30 seconds for it to reach 99 mpg. It will go from whatever I've been getting with my foot on the gas, to about 20 mpg more, then another 20 or so mpg to 99 mpg. I wouldn't this were odd, except that it's a change from the way it used to behave & I haven't changed when/where I tend to coast. Should I just ignore it? Thanks!
You can thank the cold weather for this. I suspect you either have a short drive and/or use the AC set to a pretty warm temperture. The ICE must run much more both during the prolonged warm-up phase and during normal driving (to a lesser degree). Since the ICE is running your MPG will usually not show 99.9mpg. Some of us have installed an Engine Block Heater which dramatically shortens the ICE warm-up phase and allows those 99.9mpg coasts much sooner. Also, if you and your passengers can tolerate it, turn down the AC to around 67 degrees. If you're wearing a coat and gloves this is a pretty comfortable temperture and puts fairly minimal demand on the ICE. Finally, be sure to check your tire pressures. As the weather gets colder you tire pressure will drop ~1psi per 10 degrees (rough est.). Pump them up as high as you're comfortable with (around 42f/40r is what many of us MPG freaks use) and be sure to adjust them frequently as temps change. This will reduce your rolling resistance when coasting and reduce ICE demand and allow shutdown sooner.
