MPG for first 5 min of trip?

Normal. All cars burn a lot of fuel warming up the engine and catalytic converter, and the Prius is no exception. That's the main reason short trips are so hard on mileage.

Tom

 

So, would I be better off letting the ICE come on during the first 1/4 mile (mostly downhill) of my commute than doing it in EV mode, and having the ICE come on when I hit the flat stretch (a bit of stop and go, and then I start my P&G)?

 

Yes. EV mode is never a good idea, unless you are moving a short distance at low speed, such as around a parking lot, or under some very special circumstances where you know your battery is going to be heavily charged in an upcoming downhill.

Tom

 

I've found that to get the best mileage when the engine is warming up, you need to reach 35+ mph and stay at a relatively constant speed without much stopping and starting. If you can do that, mileage will be 45mpg+. For example, if I hit all the green lights on the surface streets on the way to the freeway, I'll get 45mpg. If I get stuck at a couple lights, I get 25-30mpg.

Unfortunately, most commutes start at slow speeds with a bunch of starting and stopping so I typically get 25-30mpg the first 5 minutes.

 

Evan -

Even at stop lights?

I have quite a few stop lights in the beginning of my drive. I find that when I use the EBH in the morning, the ICE is warm enough that I can use the EV button to kill the ICE and prevent idling at these stop lights. (Without the EBH pre-warming I typically get the triple beep "cannot change to EV mode now" message.) I've been under the impression that it's better to prevent the idling, even if that delays the warm-up a bit.

What do you think?

 

I don't have an NW20 to test but with my NHW11, slipping the car into "N" cuts the fuel consumption during warm-up in half without extending the warm-up. Once combusted, the hot gas doesn't really spend a long time in the cylinder and exhaust manifold. The rate of temperature increase is more a function of the thermal properties of aluminum and the coolant.

Bob Wilson

 

No, I didn't mean to restrict my comment to the first five minutes, but by EV mode I was referring to manually forcing EV, not when the Prius does it on its own. I did qualify it with some special circumstances, which is basically any time it's better to not have the engine start because of future conditions. The control system has no knowledge of upcoming events, so it bases its decisions on existing conditions. It doesn't know that you are just driving across the parking lot, or are going to head down a big hill in ten seconds. Those are the sort of conditions where manual EV will actually help. There aren't many of them. In the hands of most drivers, a manual EV button will hurt mileage instead of help.

Tom