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Old 02-21-2009, 03:09 PM   #72 (permalink)
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Join Date: Feb 2009
Location: Georgetown, KY
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Redbox - '86 Honda Civic Si
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Originally Posted by Formula413 View Post
Sort of on topic here, I had an opportunity today to compare fuel economy with the engine cold vs warmed up. Reason: I forgot my keys and phone at home. Anyway, on a cold day my 5.5 mile drive to work usually results in about 22-23 MPG. The engine reaches normal operating temp about halfway through. Before I left for work for the second time (with the car now fully warmed up) I reset the SGII, and then checked it when I got to work. Result: 27 MPG. A rough calculation says that a $33 block heater would pay for itself in two years, at current fuel prices. Although that assumes a fully warmed up car, and from what I've read this only gets the coolant up to around 150*F. But throw in the comfort factor and the reduced CO2 output and it's a no brainer.
My back-of-napkin calculations show that a block heater will actually cost you money. If you drive to work 5.5 miles @ 23 MPG, and spend $2 for fuel, you will spend 48 cents one way. If you can do it at 27 mpg you will spend 41 cents. I'm assuming that you wouldn't be able to plug your heater in at work, so it looks like you would save about 7 cents per day in fuel costs. My best guess is that it takes about 10 cents of grid electricity to warm your car up in the morning, so you'd be spending 3 cents a day. If you could plug in your car at work you'd be saving 4 cents.

Now you also have to consider the facts that a block heater won't heat your car to operating temps and it will certainly be much less effective in the summer months, so I don't think that there would be any payback at all for your situation if you were allowed to plug it in at work. Besides, if you leave it plugged in all day at work or at home instead of just when you needed it, you'll end up wasting huge amounts of energy, so you'd have to buy a 15 amp timer or just be really good at pluggin it in an hour before you want to drive. If you want one for comfort that's one thing but I doubt you'll really save any money by using one. If you had a longer commute it might pay off.

Does anyone have any real data on reduced wear and tear by using a block heater? That could be the icing on the cake argument to make one of these make sense for most people.
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