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As the winter moves in, and my first couple of miles of the day get worse, I've been considering getting a block heater. Always curious, I developed a test to see how bad the mileage really is on a cold vs. warm engine. One short block from my house is a street with at least a half mile straight before the first stop sign, and low enough traffic, uninterrupted 30 mph runs should be possible.
So this morning, notebook in hand, I jump in the car, fire it up, and immediately head to the street, logging the engine temp. en route. At the stop sign, I check traffic, turn right onto the street & briskly accelerate to 30 mph, set the cruise, then find a landmark to reset the "trip" on the ScanGauge. Maintain 30 mph for the half mile until nearing the end stop sign where I read the ScanGauge & prepare for a turnaround. Log the "ending engine temp" & head back to the "starting end" again. I kept repeating this, using the same "cruise" set, starting & stopping points, until the temps and mileages started stabilizing. Winds stayed calm and outside temp. stayed the same (around 39 to 40). Results were:
start temp - mpg - end temp
29 - - - - 15.7 - - - 69
107 - - - - 18.3 - - - 132
150 - - - - 22.1 - - - 159
164 - - - - 23.4 - - - 166
166 - - - - 25.1 - - - 170
170 - - - - 25.1 - - - 172
172 - - - - 26.2 - - - 172
172 - - - - 26.2 - - - 172
172 - - - - 26.2 - - - 175 (would have stopped here, but temp went up)
175 - - - - 27.0 - - - 175
175 - - - - 27.4 - - - 175
175 - - - - 27.2 - - - 175
175 - - - - 27.7 - - - 175
175 - - - - 28.5 - - - 175
- - - - 27.7 - - - 175
This clearly shows the mileage increasing as the engine (and other parts) warm up. I didn't think to time it, but it must have been a good hour, therefore I think the car was pretty thoroughly warmed-up by the time I quit.
I intend to do this test at least once more, maybe twice, before installing an engine heater. Then I'll have a baseline to compare my mileage with "pre-heated" engine to.
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