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Old 01-27-2008, 09:07 AM   #11
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I would recommend driving it real nice and easy for the first 2-3 minutes.
That's likely your best bet.

Because...
The only time a block heater is effective is when the climate is so cold that the oil gels and the battery doesn't have the power to turn the engine, and the only reason this is considered effective is because the car will not start any other way... However, any other reason for it we're just dumping saved fuel money into the electric bill and then some.

Even 1,500 watts is not enough to make a difference, it provides just enough heat into the oil pan to keep the oil semi fluid in sub freezing temperatures but the entire area under the hood is hardly what I would call insulated for the purpose of actual heating. So there's a small pool of semi luke warm oil down in the sump but the rest of the engine is and stays frigidly cold even when left plugged in 24-7.

Might as well stick a 1500w space heater on the front porch and run it 24-7, that is pretty close to how effectively the heat under the hood of a car is dispersed into the atmosphere, and these things consume kilowatt hours.

To understand kilowatt hours it's simple: Take any appliance that consumes 1,000 watts and run it one hour, you have just consumed 1kwh. Run it 24-7 and we're talking roughly 720 kwh a month, I would be willing to bet most electric bills average around ~1,500 kwh a month so +700 kwh's is going to make a difference in the bill few will fail to notice.

By the time we get enough heat to actually create some warmth we're consuming so many kilowatt hours I would dread seeing the electric bill even more than I hate filling up gas, but it's either big enough or it isn't... Either way it's not cost efficient, other than purely for increasing mpg it will cost more to use a heater than if we don't.
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Old 01-28-2008, 04:04 AM   #12
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Open thermostat? No way is this an open thermostat issue. He didn't say it didn't get hot, just that it gets bad mileage.

I'd be ecstatic about the mileage you are getting. Most cars get around 1/3-1/2 hot mileage in winter and a little better in summer. I'd be surprised if I see better than 9-12mpg my first 3-4 miles. I average 22.5 60/40 city/highway on my 12 mile trip to work.

There isn't really a way around this except for pre-heating the engine. The clearances are really loose, oil thick and atomization lacking so badly on a cold engine it's amazing most of them run as well as they do.
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Old 01-28-2008, 05:23 AM   #13
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Quote:
Originally Posted by 8307c4 View Post
I would recommend driving it real nice and easy for the first 2-3 minutes.
That's likely your best bet.

Because...
The only time a block heater is effective is when the climate is so cold that the oil gels and the battery doesn't have the power to turn the engine, and the only reason this is considered effective is because the car will not start any other way... However, any other reason for it we're just dumping saved fuel money into the electric bill and then some...
I agree with the first statement: driving it real nice and easy for the first 2-3 minutes.

However with all due respect, I take exception to the rest.

Until recently when fuel cost has become a real concern, its true that the only use for a block heater was in frigid temperatures where an engine would not start otherwise.

However we who track fuel economy seriously have learned that an engine is much less efficient while warming up. And those who have installed block heaters or tank type heaters have been able to document improved fuel economy. They have also documented that the cost of the electricity is far less than the cost of the fuel saved by using the heater.

There are several reasons:

#1: You described a process where the oil at bottom of pan is warm and the rest is ice cold. This is not how a block heater operates, you've instead described the operation of an oil pan heater which is not under consideration in this thread. We're discussing block and tank heaters which warm up the coolant and thus the block. Heat transfer to the block is very efficient, though granting the losses due to lack of insulation. Those losses are the same regardless of how you warm up any given engine so I won't consider them.

#2: The cost per BTU, or cost per energy unit, of electricity is far lower than that cost for gasoline or diesel fuel.

#3: Following from the lower cost of electrical energy, the job of warming up the block is less expensive when you use wall current to do it. Otherwise, you're basically burning fuel to create heat to heat up the block.

#4: The engine itself operates at lower efficiency during warmup due to the richer mixture that's needed when the block is cold. The sooner you can get the block up to the temperature where it can operate at its optumum air/fuel ratio, the better the fuel economy will be.
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Old 01-28-2008, 04:35 PM   #14
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For the record, two hours with 1000W tank heater on, with 25F ambient, brings my motor up to full operating temperature. That works out to 2kWh/18 cents. Now even if I only save 18 cents worth of gas by doing this, I have a car that is easy to start with defrost heat at the ready.

Tank style heaters work very well, saving fuel, saving time, saving emissions.
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Old 01-28-2008, 05:18 PM   #15
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hot air intake may help with little cost.
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