How long should I warm up my Toyota Prius C, or do I need to?

The Prius warms itself up. There is nothing special that you need to do. That is, when the engine first powers up and you start driving, even though the instrumentation shows that the engine is powering the wheels it's really not. For the first couple of minutes, unless you do something silly like flooring it, you are running in EV mode. You can verify this with a Scangauge. Looking at the ignition timing display you'll see the timing is negative during this warm up period. When the gas engine is actually powering the car the ignition timing will be positive.

Sitting while the engine warms up just wastes gas and provides no benefit.

Some of the things that are true in an old fashioned car are just not true in the Prius. For more information, consider joining one or more of the Yahoo Prius groups. Priuschat is also a good source of information.

2004 Prius MPG from the logbook. (Complete years only):

2003-2004 -- 50.8 mpg 17,628 miles

2005 -- 52.6 mpg 14,688 miles

2006 -- 56.3 mpg 16,174 miles

2007 -- 57.3 mpg 18,384 miles

2008 -- 59.9 mpg 21,755 miles

2009 -- 61.4 mpg 16,177 miles

2010 -- 65.2 mpg 12,134 miles

2011 -- 66.9 mpg 11,272 miles

-30 seconds is sufficient for any new (less than 5 years old) gas or hydrid drive car to idle (any longer and all you're doing is running the defrost heater and burning gas)

-I don't have any experience with any of the Prius family, but Toyotas and most cars in general have a temperature gauge, or at least at cold or overheated coolant indicator; use this to tell you just how long it takes to warm up the engine (good thing to look up in the owner's manual)

-in general, no amount of idling will effectively "warm it up", it can take over 5 min of driving for the engine coolant to effectively get to operating temperatures

-the transmission is just as important and only gets warmed up through use ie driving, while idling that simply does not occur

-until it is at regular operating conditions, fuel economy and to a lesser extent performance will be reduced

-just drive with a light foot for the first few minutes (brakes as well as gas unless until you are familiar with how they work while cold)

-trying to gun it while cold will cause engine damage over time (idling wouldn't prevent that) so just relax, in general driving conservatively improves fuel economy anyway and I doubt you bought the Prius for drag racing anyways

it's not the coolant that needs to come up to operating temps, it's the internal bearing/surface clearances. metal expands when heated. this is factored into the manufacturing of components. to meet optimum pressure/flow specs for lubrication, some sort of warming of an engine is needed. at least the amount of time it take to adjust mirrors and fasten belts.

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but in this case, Jerry has it spot on. thumbs!

the gas engine doesn't deal with any load apps at low speeds unless you go crazy driving right off. so you can just start and drive instantly. no wear on the engine over the life of the vehicle. unlike non-hybid vehicles.

Put firewood and gasoline underneath it then light it and wait an hour and it'll be nice and toasty