Since it's gotten cooler, I've been seeing the Coolant Temperature light coming on when starting the car. The light goes off after a few minutes. However, I've noticed that the ICE is not shutting off as much as it was the first day that we had the car. Talking a temperature change of at least 15 degrees. I could sit in the driveway with the car on and in a few minutes the ICE would shut off. Now after five minutes the engine is still runnin. The power screen does not show the engine charging the battery. Is anyone else seeing this situation? Wondering if the cool weather is keeping the ICE from shutting off.<br><br>Tom

I have noticed this same behavior, but don't have an answer why. This week has been 55-65 deg. F, whereas it had been 70-80. Cause-and-effect? I don't know.<br>Sam Williams

I'm thinking that it likely has to do with the temperature of the coolant. Maybe the system is using the ICE to raise the temperature of the coolant warm enough to heat the car if needed? I didn't have the fan on though.<br><br>Tom

Hey maybe that is why we have only been getting 45mpg (imperial), the gas engine runs longer at startup everyday for the last 45 days. <br><br>We park our car in the garage where it is always cool and the cool temp light has always come on and stays on at startup.<br><br>Interesting.

"raise the temperature of the coolant warm enough to heat the car if needed"<br><br>I was told by the dealership it has an electric heater so we would have instant heat at startup in the Winter. Hope this wasn't mis-information cause it would be REALLY nice.

The "electric heater" is mis-information - not unusual for dealers. The Prius heater is conventional in that it relies on the heat of the engine coolant.<br><br>On this site, Priusman said: "The gas engine stays on initially until coolant reaches operating temperature and main battery pack at a certain SOC [state of charge] level. After warm-up the THS will begin optimizing for the best combination, and of course you'll have heat for the cold mornings......Priusman"<br><br>I was very pleased to find that the car provides heat 2 minutes after starting, which in my experience is fast. This is likely due to the fact that the engine is small - less metal to heat up.<br><br>Sam Williams

I am skeptical that colder ambient temperature is the only reason for the ICE running longer at startup. Most auto coolants run at 170-180 deg F. and the difference between starting at 55 deg. or 80 deg. is pretty minimal. Perhaps "ee" will swing by and help us with this one.<br><br>Sam Williams

Since you asked, as previously noted coolant temp and battery SOC are the criteria. One possibility may be that it seems longer. I know I have a tough time estimating time, especially early in the morning. Another possibility is driving mode. It take a lot longer for the coolant to come up to temp at low load than if working harder (that is not a recommendation for WOT acceleration on a cold engine!). The other possible is a lower SOC from previous operation, although by my observation coolant temp usually sets the time. <br><br>Hope that helps.