Block heater to improve mpg

Yes it does. This is a very much talked about subject. Search the site again and you will find many threads and documentation about this.

 

+1

The 1st 10 minutes of driving can easily achieve +50mpg when you start out already warmed up, whether summer or winter.

 

I also agree. I run mine year 'round in pretty much the same climate as yours.

As for searching, the forum software's native search function leaves a little to be desired. You might instead try Google.

 

Not worth it.

Of course, if your engine block heater uses less power and/or is on for less time, or the cost of gas goes up, the math may change.

Assumptions:
Engine block heater consumes 500W
Is on all night (16 hours)
Total Power consumption: 8 Kwh
Estimated Power Cost: $0.40 to $0.70

Getting 50 MPG vs 30 MPG on a 7-mile stretch saves 0.093 Gallons of fuel, for a cost of $0.28 at $3.00/gal.

So, the money you spend to power your engine block heater is greater than the fuel savings.

Electricity can heat the engine more efficiently than the ICE, but if you keep your heater on all night, when you aren't going to use the car, the heating serves no purpose. Now, if you have the engine block heater on a timer to come on an hour or two before your morning commute, it might be more efficient.

-->Adam

 

I think the EBH saves, slightly. 16 hours is way too long (4 hours is more than sufficient), and the OEM heater is 400W. In the other direction, your electricity cost seems to be too low ($0.11/kWh per DOE). Comes out to about $0.25 using gas (@$2.65/gal) and $0.18 using EBH.

ETA: I didn't factor in the cost of the EBH. Assuming all prices stay equal, you'd have to make about 900 trips to cover the overhead.. about 3 and a half years of full-time commuting.

 

16 hours? Er, you don't have an EBH, do you. Otherwise you'd know, you only have to run it for 90 minutes or so, on a timer.

 

3 hours is suffiecient for most applications.

Normal start WT if block heater not used is 90F
1 hour EBH 110F
2 hours EBH 125F
3 hours EBH 135F
4 hours EBH 145F
all night EBH 150F

This has been my experience.

 

I found it made a significant difference in my Gen2 during the fall through spring months. I didn't use it in the summer, because I didn't think it was really necessary.

Having it on for two hours in a non-heated garage, when the outside temps are around 5F adds more than just mileage. When the temps get down to below freezing, I'll usually turn on the heat (I don't really need it for a short commute; different story when I'm on the highway in the winter). The EBH also means you get real heat MUCH sooner. How do you measure that advantage?

 

I can't believe you couldn't find millions of threads on this issue. first of all, if (and when) you get an EBH, put it on a timer to come on about 3 hours prior to your leave time. you do NOT need to leave it on all night. YES, it will make a substantial difference in your mileage year 'round. try the search again for EBH, engine block heater, etc., or just search threads for FireEngineer, as he personally installed most of ours here on PC, and probably more than anyone else has anywhere.


**edit

Kirk, I just saw you are in Raleigh. It will make a difference even there, even in the summer time. Its a real advantage on the short trips.

 

Above 50F ambient a timer for 2 hours.

Between 50F and 20F a timer for 3 hours.

Below 20F, as long as you can.

Wayne

 

FYI- Studies in Canada have indicated that anything more than 4 hours is a waste.

 

Do you have any reference on this? I would like to make a business case for pluging it in or not, and for how long, based on outside temp. Electricity here is cheap (about 7cent/KWh) and pretty much green (hydroelectricity) but still I want to do something logical.

 

The Canadian studies are based on "normal" block heaters, which run from about 600W to about 1.5 kW (my Subaru had a 1 kW, and at -50C ambient, parked outside, with the block heater on all night (motel), I had warm air out of the heater when I started the car! I DID have great problems getting it to move, however, as all the diff and trans fluid was almost solid!

I find the 400W Prius block heater rather anemic. In -20C weather it does get the coolant above freezing, but just barely. Even all night operation in a garage results in coolant of about 10-15C. Still, better than coolant at -20C! The thermos is pretty much useless.