Quote:
Originally Posted by redpoint5
It uses fuel and runs the engine at least until reaching a coolant temperature of 130. The car could simply require more brake effort to mechanically waste speed into heat, but instead the car starts up for no reason that has been adequately explained to me.
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Isn't it like, oft repeated wisdom that using your brakes for long downhill stretches risks overheating the brakes and losing braking force altogether? Which is why it is recommended to use engine braking instead. When the Prius's battery is maxed out, it will have to use friction brakes and the car would rather not rely on it for long.
As for why it uses fuel to heat up the coolant, maybe the ECU detects that the engine has stayed off for so long the coolant was cooling off below a threshold, which needs heat to keep the Cat working and lubricant flowing. I dunno without flipping through the readouts with you. I know my car likes keeping the engine on for longer than it need be to get the engine temp to at least 70. It shouldn't need to heat it up to 130 to be hot enough but who knows why Toyota chose that temp.