Why install a engine block heater when you buy your Prius

As I understand the Pruis engine the colder it gets the longer it takes for the Gas engine to warm the car up which effects the cars ability to switch to electric and lessens the MPG. With that in mind one could easily plug the engine block heater in on a timer and as the weather gets colder you could set it to come on a couple hours in the morning before you go on your first trip.

This would especially help those of us where it gets cold for months.

I've had one since my 2009 purchase. I really notice the difference in the first 5-10 minutes in mileage if I forget to plug it in for my first trip.

Uhh... so whats the question? You basically answered your own question in your post...

I might note that the effects of a EBH may be diminished with the 2010 prius....

So why would the effects of an EBH be diminished with the 2010?

Another question, is at what temperature does it begin to make sense? Obviously its good to pre-heat if its below freezing outside, but does it make much difference if its in the 40s or 50?

Seems like a waste of energy and effort. The extra couple of minutes to warm up--how much gas does that take? It's not like the electricity for a block heater is free or the cost of the heater or trouble installing it, plugging it in, etc.

In here it’s recommended to use block heater when outside temperature is less than 5 degrees Celsius (that’s 41 degrees of Fahrenheit).

We have lot of university studies about this in Scandinavia. Don’t know is there any of them in English...

Well I live in winter country (it's -18C or 0F outside right now). Pearl is parked in an insulated but unheated garage. It's about -6C in the garage. In Edmonton all Prius come with block heaters. I used it a few times last winter but I don't usually bother. It doesn't have a really big effect here anyway. I suspect it works really well when your ambient temp. is between about 40F and 10F. Below that there is too much loss to convection, above not enough gain to be cost effective. Most of those who use it are mileage freaks and don't want to know how much it costs over just letting the car warm up by driving it.

To have a block heater be efficient you have to know when you're going to use the car. It takes about 3 hours for it to have the desired effect. Any longer and you're wasting energy. Any shorter and it doesn't warm up enough to make a difference (it's only a 400W heater).

I'm retired, and never know exactly when I'm going to use Pearl. So for me it's not practical to use it.

DO block the front grill. See other threads for how-tos. -I- think this has a larger effect on efficiency.

The GIII does have the advantage of the exhaust heat recovery system. The GII's thermos has no effect here when it's "normal winter". That is, when it's below about 10F the coolant in the thermos is cooled off too much to be useful when the engine is as cold as it gets overnight.

So I live with poor mileage in winter. My current tank of fuel, for example, is running at 6 to 6.5 l/100 km. In spring/summer/fall weather a typical tank runs at 4.5 l/100 km. The GIII should do about 10% better.

This depends on how important MPG is to you.

A competition hypermiler will use it even in 100 degree weather, because that is still far below the engine operating temperature. But many, perhaps most regular commuters won't ever find it worth the hassle.

There is not only measurable effect on MPG but also on engine wear. But, I would use it only in very cold weather on only couple of hrs before a trip.

Does anyone have much experience with Circulating Tank Heaters? They are 1500 Watts, rather than 400, and I have heard they can heat the coolent up to 160 F, while the EBH tops out at about 110 F. The Circulating Tank Heater plumbs into the heater return hose, so the closed coolant thermostat does not stop the circulation. I believe the circulation is created by hot coolant rising, and over time, this creates a flow though the cooling system without needing a pump.

I have been trying to generate some discussion, but maybe not many people have experience with thes Circulating Tank Heaters.

Products such as $40 Kat's 13150: [ame="http://www.amazon.com/exec/obidos/ASIN/B000BQUUR6/ref=nosim/priuschatcom-20"]Amazon.com: Kat's 13150 1500 Watt Aluminum Circulating Tank Heater: Automotive[/ame]

or the $65 ZeroStart 330-8003:
TANK TYPE ENGINE HEATER 1500 WATT | StreetPerformance.com

Anyone have experience to indicate the Zerostart is worth the extra $30?

Not sure about the complex coolant system of a Prius. The GenII with the heat control valve such a circulating heater would be impossible to use

The Temro/Zerostart circulation heaters used to be VERY popular up here and in general work far better than frost plug or especially the convection heaters used by Toyota

A 1,500 watt circulation heater, if it could be used in the GenIII Prius, would be huge overkill for a 1.8 litre motor. I used to have a 1,000 watt version in a '84 Chevy work truck with a 350 V8, and even at -40 with a strong wind the hood would be completely bare of frost - instant start and instant warm air out the defrost

You would use a 1,500 watt circulation heater on something like a large diesel engine. Temro used to offer circulation heaters of 600-800 watts, that size worked well even on big V8's

Well Jay, I had a Subaru with a 1500W frost plug type heater. Yup, it worked very well!! Only used it once, parked overnight at Blue River in BC. It was -50C the next morning. Got in the car and it started right up and blew warm air! Stalled it three times trying to get it to move. The transmission and both diffs. were filled with solid oil! Had to drive at 15 km/hr for a few minutes to warm them up.

The circulating type heater uses a solenoid to pump the coolant through it. You can hear them cycle. It would work very well as long as there is no valve closing happening in the GIII in the bypass/heater circuit. Check the shop manual or look and trace the hoses.

-I- wouldn't run it for more than an hour before driving away. And I agree, a lower power version would be better suited to the Prius.

The Temro circulation heater doesn't use a solenoid, it uses a couple of check balls with a spring. As the coolant heats in the chamber, it expands, forces the outlet check ball off its seat and against its spring

Hot coolant exits, cold coolant is drawn past the inlet check ball which then closes. Cycle repeats, which is why you hear that soft "chuff chuff chuff chuff" sound when it's plugged in. And why there are arrows on the unit that indicate which way is up, get that wrong it won't work at all or not very well

I've used the Temro circulation heaters on large diesel equipment with great results. For the life of me, i can't understand why a person would not plug in a diesel motor

They sit there grinding away on the starter, when it does start it runs quite poorly. Even modern diesels have very rough cold starts, especially -20 F and colder

Any motor benefits from a preheat. The colder the temps, the more beneficial the preheat